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Naval Encounters (3pp)

Running Lightweight Naval Encounters

Not all naval encounters need to end in combat, but sometimes a sea battle is the only resolution. This framework can be used whenever your players have set sail and end up running into a variety of naval encounters.

1) Set The Environment

Those traveling the sea know a change in the weather can be the difference between a smooth passage or going to Davy Jones’ Locker. Tell your players what they see, hear, smell or feel. Make sure the players know the current weather, visibility and state of the seas at the start of any encounter.


To save time at the table, you can determine the weather yourself during prep time or randomly roll the weather using the tables found in the Random Sea Weather sidebar. Some other considerations:

  • Low winds have a 25% chance of creating a dead calm, halting movement and requiring rowing or magic to move.
  • High winds can increase the speed of a ship sailing with the wind by 50% and reduce the speed of a ship sailing against the wind by half.
  • A storm is present when weather conditions see both strong wind and heavy rain, with a 25% chance of a destructive tropical storm resulting.

Random Sea Weather

These charts are intended for typical sailing weather in subtropical and tropical seas and lean towards producing favorable sailing conditions. I would adjust the chart for cooler climates or greater simulation.

d20 Temperature
1-12 Normal for the season
13-16 1d10 x 2 degrees Fahrenheit colder than normal
17-20 1d10 x 2 degrees Fahrenheit warmer than normal
d20 Wind
1-12 Light
13-16 Low
17-20 Strong
d20 Precipitation
1-14 None
15-17 Light Rain
18-20 Heavy Rain
d8 Wind Direction
1 North
2 Northwest
3 West
4 Southwest
5 South
6 Southeast
7 East
8 Northeast


For the visibility and state of the seas, make a judgment call based on the weather.

  • Strong wind creates high, rolling seas, reducing visibility.
  • A calm sea and clear sky offers great visibility from the crow’s nest, with the ability to spot another ship up to 10 miles away, overcast 5 miles, rain 1 mile, and fog 100 to 300 feet.

State of the Seas

Don’t forget to describe things like the color, clarity, depth or obstacles of the sea itself. Let them know if they are sailing:

  • Over a clear, shallow sea full of wrecked ships
  • Through shallows with jagged rock or coral reefs
  • Through debris such as seaweed or floating wreckage on a boiling sea of huge waves, crashing into their ship on deep blue water with nothing but the wind at their back

2) What Ships/monsters Are Involved?

The sea is a vast wilderness full of perils above and below the waves. Sailing across the seas can get boring without some encounters. You can decide on a set encounter or run a random encounter.

Once you decide that an encounter will happen, ask the following:

  • Do the players see any of the ships/sea monsters?
  • How far away are the ships or monsters?
  • What direction are the ships or monsters heading and at what speed?

Making Knowledge Checks

If players ask to learn more about an approaching ship or sea monster, ask for a skill check with a Difficulty Class (DC) based on available clues they can sense. It might be a good idea to combine a Wisdom (Perception) check with one of the following:

3) Determine Player Intent

Now that the players know the conditions of the seas and what potential threat is in front of them, ask the players what they want to do. Even though their PCs are beyond attack range and out of combat, there are plenty of actions available to your players.

When your players notice another ship at long range (beyond the range of cannon and attack magic), they could consider the following options.

Chase (or Flee). If your encounter turns into a chase, avoid having the encounter becoming long and drawn out. Determine how many rounds it will take to close in on the quarry, and fast forward to the excitement.

Convert rounds to minutes, or multiply travel distances by 10 until you need to zoom in on the action. A chase on the water is just a chase between ships (or a ship and sea monster). Try introducing complications to sea chases, such as those found in the Sea Chase Complications table, which provide complications for a ship’s pilot.

Scan. If your players glimpse a far off object, have them make Perception checks. If they attempt the check with a spyglass, from the crow’s nest or while flying above the ship, have them roll with advantage.

For a ship, they could find out its type, the flag it is flying, or if it is damaged. For a monster, they could determine its general shape or behavior. Any further information should require additional checks (see Making Knowledge Checks sidebar).

Table: Table: Sea Chase Complications
d20 Complication
1 Your ship finds itself in the path of a small whirlpool. Make a DC 15 Wisdom (Vehicles – Water) check to navigate the hazard. On a failed check you momentarily lose control of the ship. The ship’s speed is reduced to 0 ft. and the ship rotates 90° (odd = clockwise, even = counter-clockwise).
2 Your ship is hit hard by currents in all directions as the sea suddenly swells around you. Make a DC 10 Wisdom (Vehicles – Water) check to navigate through the swollen sea. On a failed save, your ship’s speed slows by half.
3 Your ship finds itself traveling through thick seaweed. Make a DC 10 Wisdom (Nature) check. On a failed check, you are unable to find a clear path through the seaweed and your ship’s speed slows by 30 ft.
4 A sea monster joins the chase. Roll a random encounter or pick your own monster.
5 A coral reef blocks your path. Make a DC 10 Wisdom (Nature) check to find an alternate route. On a failed check, your ship’s speed slows by 30 ft., and your ship takes 4d10 slashing damage.
6 Jagged rocks block the path of the ship. Make a DC 10 Wisdom (Perception) check to find an alternate route. On failed check, you ship’s speed slows by 30 ft., and your ship takes 4d10 piercing damage.
7 A large swell or wave is headed your way. Make a DC 10 Intelligence (Vehicles – Water) check to successfully navigate the wave. On failed check, your ship’s speed slows by 30 ft. and your ship takes 4d10 bludgeoning damage.
8 A sudden, massive gust of wind blows against the ship, regardless of the current wind direction. Make a DC 15 Wisdom (Vehicles – Water) check to maintain control of the ship. On a failed check, you momentarily lose control of the ship. The ship’s speed is reduced to 0 ft., and the ship rotates 90° (odd = clockwise, even = counter-clockwise). The wind direction quickly returns to normal.
9 The wind suddenly drops off, your speed is reduced by half, and you find yourself entering a dead calm. Make a DC 15 Wisdom (Survival) check to find the wind. On a failed check, your ship’s speed is reduced to 0 ft.
10 Patches of fog rise up out of the sea all around you. Make a DC 15 Wisdom (Survival) check to find a clear spot. On a failed check, your visibility is reduced to 200 ft.
11-20 No complication.

Hide. If your players want to hide their ship, consider the conditions and geography. Ships that are have cover from darkness, tough weather or a jagged coastline can easily hide, but clear weather in the open sea should make hiding impossible.

Wake Drop. If your players are being chased, they have the options of dropping fire barrels or other items in their wake. This action is intended to force the pursuing ship to either risk taking damage or detour and take another course.

Hoist a Flag. Most ships fly a flag at the top of their main mast to identify themselves. Your players could hoist any flag they have in their inventory, using the flag to appear as an ally, identify themselves as pirates, or even surrender. If your players are attempting to deceive an enemy, have the opposition make a contested check to see through the deception.

Use Magic. Casting protective spells before getting into the range of cannons and attack magic is usually a good idea. Teleport, various divination spells, gust of wind, and other magic that can be cast from far away can come into play here as well. Reward players who come up with creative ways to use magic.

4) Determine Ship/Sea Monster Intent

  • It is easiest to figure out the intent of a ship using an NPC such as the Captain as your focus.
  • You can predetermine the intent of each NPC or decide after the players make their intentions known.
  • Most of the options in Determine Player Intent can work for NPCs as well.
  • If your NPCs have access to spells, don’t forget to use them.

Sea Monsters

Hostile monsters should do whatever is in their nature, such as defending their territory, protecting their young, hunting for food, or demanding treasure as tribute.

5) Run The Encounter

It’s finally time to run the encounter. Think of the encounter as something evolving and to ask your players what their intention is as things progress. Keep track of your NPCs/monsters intent as the encounter progresses. The encounter could turn into a chase, a parlay between captains on a nearby beach, or any other number of non-combat scenarios. If a combat scenario occurs, remember that running naval combat is just regular combat with some additional considerations which are outlined below.

Rolling Initiative

Just like regular combat, If either side decides to get hostile, it is time to begin combat rounds, regardless of the distance between the parties. You can set these rounds to be longer, such as one-minute rounds, if the parties are at long range.

If any of the parties are in attack range, aware of each other, and hostile, then roll initiative. However, the following additions and exceptions apply:

  • All ships have an initiative of 0.
  • Ships can only move and are controlled by the pilot on their turn in the initiative order.


The distance between parties in an encounter can make an encounter long and drawn out. Try to fast forward to the excitement by checking for actions at each range. Ask yourself, ‘How far away can the players or NPCs/monster fire at an enemy with weapons or magic?’.

It is up to you to decide how many weapons could actually be aimed at a boat, if it is in range due to the facing of each vessel. Try to break up the time is takes to close in on each other to the following ranges:

  • More than 2,000 feet: Outside of attack range, see Determine Player Intent
  • 2,000 ft. – 1,200 ft.: Far range of heavy cannons (disadvantage)
  • 1,200 ft. – 600 ft.: Medium range of heavy cannons (disadvantage) and far range of some siege weapons.
  • 600 ft. – 250 ft.: Heavy cannons fire with accuracy and light cannons fire with disadvantage. Most siege weapons start to be in range. Some ranged weapons such as longbows will start to be in long range.
  • 250 feet and closer: Cannons, siege weapons, ranged magic, and ranged weapons are all in range, and combine to make any encounter at this distance potentially deadly in a very short period of time.

Grid Or Gridless

All the specifics of positioning boats can be a bore or over the top for some players, while others love the tactics involved. Naval encounters can be run without a grid, but having some kind of markers on your tabletop to show the distance and facing of ships is a good idea, even if it is just scratches on a piece of paper. Even without combat, the encounter might involve skulking or chasing, so keeping track of range is important.

If you are using grid combat, you should avoid the grid until the ships are close enough to each other to attack. If you have a big enough table or screen, start to place the ships once they are inside the long range of whatever weapons are able to attack. For groups that are interested in being specific and exact with details, bring out the grid and markers.

If you are going gridless, It might be a good idea to quickly sketch out ship placements, indicating speed, heading and facings for your players. For groups where a narrative style will work best, go gridless.


Sailing ships are floating on water and take time to accelerate and decelerate. Use the following guidelines to determine ship movement:

  • The distance a ship moved the previous round is its velocity.
  • If a ship ended the previous round with a speed of 0 feet, then the current velocity of the ship at the start of the round is 0 feet.
  • As mentioned previously in Rolling Initiative, ships can only move, as directed by the pilot’s action on their turn in the initiative order.


Bringing a ship to full speed takes time and your should consider the following when a pilot wants to increase the velocity of a ship.

  • When a ship begins a round with a velocity of 0 feet, the ship can only move up to half its speed that round. For example, if a ship has a speed of 50 feet and its current velocity is 0 feet, the ship can only move 25 feet that round, increasing its velocity to 25 feet.
  • A ship can move up to double its current velocity, but only up to the ship’s maximum movement. For example, if a ship has a speed of 50 feet and its current velocity is 30 feet per round, the ship can still only move 50 feet that round.


Slowing down a ship takes time and your should consider the following when a pilot wants to decrease the velocity of a ship.

  • If traveling at a velocity greater than 15 feet, a ship must move at least half of its current velocity. For example, if a ship’s velocity is 30 feet, it must move at least 15 feet that round.
  • If a ship’s velocity is 15 feet or less, it can come to a halt that round and decrease its velocity to 0 feet.
  • If a ship collides with another ship or another hazard, its speed should rapidly decrease at the GM’s discretion. See the Ramming section later in this section for more details on handling the outcome of two ships colliding.

Pilot Checks

When a player needs to make a pilot check, ask them to roll using their PC’s proficiency with Vehicles (Water). It might be a good idea to use the pilot’s passive proficiency for routine checks.

  • In nearly all cases, pilot checks should be made by adding proficiency in Vehicles (Water) to a Wisdom check
  • When visualizing the line a wave will take or similar analyses, make the check using Intelligence
  • If the pilot is ordering the crew to quickly get up to full sail, make the check using Charisma
  • When making sudden evasive maneuvers, consider making the check using Dexterity

Ship AC Alternative

As your pilot gains experience, you may want to replace the ship’s Armor Class (AC) with the pilot’s proficiency with Vehicles (Water).

Ship’s AC = 8 + Vehicles (Water) proficiency + Dexterity modifier



For simplicity, a ship heads straight in its current direction at its current velocity, unless the pilot orders a change in heading (direction) or the ship collides with another object. On the pilot’s turn in the initiative, they can order the ship to turn (rotate) as follows (without considering wind direction benefits or drawbacks):

  • Up to 45°, with no impact on velocity
  • More than 45° and to 90°, reducing velocity by half
  • More than 90°, reducing velocity to 0 feet and allowing no additional movement for the remainder of the turn In rough seas and storms, make a DC 15 Wisdom (Vehicles – Water) check whenever changing heading.

On a success, the pilot maintains full control of the ship. On a failed check, the ship rotates 90° (odd = clockwise, even = counter-clockwise).


When a pilot is ordering a heading for the ship, it is a good idea to have as many guns facing their enemies as possible. The tokens are rectangles and ships have most cannons placed on both the port (left) and starboard (right) sides of the ship.

Firing Cannons

Here are some considerations when firing cannons in combat.

  • It is best to put multiple crew on each ship cannon, since multiple actions are needed to load, aim, and fire a cannon.
  • At long range, have your players aim the big guns to keep them busy.
  • At close range, have your players without effective ranged attacks man the deck/swivel cannons and let them roll the attacks and damage. Only two crew are required to operate these light cannons, since aiming and firing are one action.
  • If no officer is in charge of coordinating the heavy cannons, the cannons fire with disadvantage.
  • Feel free to adjust the damage output of cannons down if you want to increase the importance of ranged weapons and ranged spellcasting.
  • If you running your game in a world where gunpowder does not exist, consider having cannons be arcane devices, or replacing them with ballistae and catapults.

Statistics for cannons are provided in the Equipment & Vehicles section.

Officer Actions

As part of their turn in combat, all players can complete an officer action, but players should be free to use these while outside of combat too. It’s a good idea for every PC on a ship to have their own job. They choose from Captain, Quartermaster (First Mate), Pilot, Boatswain, Master Gunner, and Ship’s Surgeon. Officer actions are explained in detail in Shipboard Roles.


Some long range spells worth taking a look at are ice storm, project image, dimension doorgate and control weather. At close range, spellcasters can cast spells to teleport, make things invisible, attack, defend, or put out fires. As mentioned previously, try to reward any creative use of magic.


Major repairs to the ship should be made when the vessel is berthed. While in port, it takes one hour of labor and 20 gp of material to repair 1d4 hit points of damage to ship. It is up the GM to decide how many hours of skilled labor are available in a day, based on the size of the port.

For emergency repairs, don’t be afraid to let a player get creative with spell use, such as using fabricate to repair a ship using debris. Cantrips such as druidcraft and mending are not powerful enough to repair a ship, but in dire circumstances, you might consider allowing a player to cast these cantrips using a 2nd level or higher spell slot (1d4 hit points of repair per spell slot) and increasing the casting time to 10 minutes.

A boatswain’s officer actions focus on repair, and can be highly effective for making emergency repairs. For general repairs while the ship is not berthed, it takes one hour of labor and 25 gp of material to repair 1d4 hit points of damage to ship. It is up to the GM to decide if sufficient materials are available to complete repairs while sailing.

Using Sections

Hit points can be abstract, especially when figuring out exactly what part of a ship damage has occurred. For more verisimilitude, consider splitting the hit points of a ship into hull sections and sails. This can provide PCs and NPCs with the ability to target specific sections of the ship, such as the sails or the rudder. If a specific section is targeted, have the attack rolled with disadvantage.

Damage To Sails

As an optional rule, you can track damage to sails. Similar to a monster taking non-lethal damage, a ship’s sails (sails, rigging, masts) can be targeted with the intention of crippling a ship, but not sinking it. A ship’s sails have a hit point value equal to 25% of the ship’s hit points. If a ship has 400 hit points, disabling its sails requires 100 hit points of damage. This is a separate pool from the ship’s hit points.

If a ship takes 50% of its maximum hit points in sail damage, its speed is halved, and pilot checks have disadvantage. If a ship takes 100% of its maximum hit points in sail damage, it is immobile.


To ram a ship simply requires a pilot to hit their ship into an enemy ship.

  • The attacking ship must be able to reach the enemy ship using its move.
  • If the defending ship has limited mobility, the attacking ship’s pilot gains advantage on their attack roll.
  • Attack: 1d20 + Vehicles (Water) proficiency + your Dexterity versus the AC of the other ship or contested by the pilot on the other ship (your choice). If the attacking ship hits its target, the velocity of the ramming ship becomes 0 feet.
  • Damage: Velocity of Ship (in feet per round) x 1d4 bludgeoning damage and the ramming ship takes half of the damage to itself. For example: 30 ft. x 1d4 (rolled 3) = 30 x 3 = 90 points of bludgeoning damage to enemy ship, 45 points of bludgeoning damage to the attacking ship.
  • If the attacking ship has a ram, increase the damage taken by the defending ship and reduce the damage taken by the attacking ship. See Ram in Ship Modifications for specifics.
  • When a ship is rammed, creatures on board the defending ship roll a DC 15 Dexterity saving throw. On a failure, they take 1d6 bludgeoning damage, or half damage on a success. For a more violent crash, increase the damage to 2d6.


To board another ship, as a bonus action, an officer needs to order the ship to be brought up against or alongside an enemy ship, with the goal of capturing or destroying it. The easiest way to think about boarding is to treat it as a big grapple attack.

  • To board an enemy vessel, the pilot must first approach the enemy ship, using any of the ship’s movement required to close the distance.
  • The base DC for a boarding check is 10. If the boat has a speed of 0 ft., the check is made with advantage. If the other ship is under full control and evading the attacking ship, make a contested Wisdom (Vehicles – Water) check.
  • Encourage your players use their own actions to aid in the boarding attack by using grappling hooks, employing boarding nets, swinging over on ropes, or dropping a bridge. You can have any of these actions provide advantage to a pilot making a Wisdom (Vehicles – Water) check. A boarded ship should be considered restrained. A ship can attempt to free itself with an opposed Wisdom (Vehicles – Water) check. If creatures use their actions to cut grappling hooks, remove nets and other restraints, provide advantage on the check.
  • Once boarding has occurred, you are ready to start running a regular combat encounter on the decks of two ships. Remind your players that there are plenty of ropes and jacob’s ladders to climb to get above deck level and holds below.

Running Aground

When a ship finds itself in water that is too shallow (a water depth less than the ship’s draft) to allow the ship to pass, it has run aground.

  • A ship that has run aground has a speed of 0 ft., and any attempt to maneuver the ship requires a difficult piloting check.
  • When a ship runs aground it takes 3d6 bludgeoning damage. If the ship was traveling at a velocity higher than 15 ft., roll additional damage equal to the ship’s velocity x 1d6 bludgeoning damage. You should also consider the composition of the material the ship runs aground on: – Sand: no extra damage – Rocks: additional 6d6 piercing damage.
    • Reef: additional 6d6 slashing damage.
    • Dock: additional 6d6 bludgeoning damage.
  • Characters on board a ship while running aground make a DC 15 Dexterity saving throw. On failure, they take 1d6 bludgeoning damage, or half damage on a success. If the ship was traveling at a velocity higher than 15 ft. and/or the ship crashes into rocks, reefs, and docks, roll an additional 1d6 bludgeoning damage.


Once a ship is brought to 0 hit points, it is considered “holed” and is sinking, with the following effects:

  • The ship can no longer maneuver and its speed becomes 0 feet.
  • All officer actions have disadvantage.
  • The ship will be completely submerged in 1d10+2 rounds. Once submerged, the ship sinks 120 feet per round, until it hits the ocean floor.
  • The ship is a hazard with flying rigging, flowing water and other chaos. The ship is difficult terrain. At the beginning of each turn, PCs make a Dexterity saving throw, with a DC set by the GM based on the nature of the hazards. On a failed save, PCs should take bludgeoning damage, be knocked prone, or even thrown into the sea.
  • For added difficulty, have swimming creatures such as sharks or water elementals attack the crew and PCs while the ship is sinking.

Massive Damage and Ship Destruction

Massive damage can completely destroy a ship.

When a ship is reduced to 0 hit points and there is damage remaining, the ship is destroyed if the remaining damage equals or exceeds the hit point maximum of the ship.

Battling Sea Monsters

When your players battle a sea monster from the deck of a ship, it is normal combat with a few considerations:

  • If your players are attacking the monster with cannons and there are PCs with officer actions available, combat rounds can take much longer and produce huge amounts of damage per round. It is important to adjust the Challenge Rating (CR) way up to compensate. Mid-level PCs could survive battles against krakens and dragon turtles with a strong ship and crew.
  • Decide if the sea monster attacks the ship, creatures on the ship’s deck, or a bit of both. If appropriate, adjust the encounter CR to handle the added hit points of the ship that the sea monster needs to damage.
  • It is always fun to have the creature disappear at the end of its turn, only to appear on the other side of the ship during the next round.

Example Encounters

Scenario 1: Privateers At Work

The adventuring party are part of a crew of privateers (or pirates if you like) chasing down a merchant ship flying the flag of a rival kingdom. As the privateer ship (Brig) closes in on the smaller merchant vessel (Cog), a warship (Galleon) flying the same flag as the merchant ship appears on the horizon.

Setting: Light rain, strong wind blowing south (+15 ft.) and rolling seas. Piloting in these conditions is DC 15 Wisdom (Vehicles – Water), and visibility is 1 mile.

Range: The merchant ship is 600 feet from the PCs privateer ship that has come out of hiding at full sail. Both ships are traveling west, with the privateer ship gaining on the merchant ship at a rate of 10 feet per round. For the encounter, the rival warship is set to appear 1 mile away after the PCs privateer ship gets within combat range of the merchant ship.

Player Intention: The players decide to chase and attack the merchant ship. Once the large warship appears and its flag is known, the players might change their intentions and decide to flee or hide. If they are able to take the merchant ship, they might try to attack with both ships, flee with both ships, or even hole the merchant ship, forcing the warship to go into rescue mode to save sailors from their kingdom.

NPC Intention: The small, slow merchant ship will try to flee and get away. If caught and combat begins, the merchant ship surrenders after one round. The warship will engage the PCs privateer ship, since the warship is from the same kingdom as the merchant ship.

Initiative: The players have initiative since they are chasing the merchant ship.

Speed: The warship and privateer ship velocity is 45 feet per round (30 ft. + 15 ft. wind). The merchant ship is 35 feet per round (20 ft. + 15 ft. wind).

How I’d run this encounter: You can worry about facing and distance or you can just let your players know when they are close enough for magic or cannons. Realistic naval combat can be lots of fun, but my players just want to know if they can fire their arrow, cannon or spell. They also really want to do things like set the other boat’s sails on fire and board the other ship. You might want to set hit points for the ship’s hull and sails individually (see Damage To Sails sidebar). Once the two ships get really close, having them ram or board will get combat to a place where melee focused PCs can shine. Once two ships are connected, you basically move into normal combat.

When the warship arrives, it might not be spotted right away. I’d check based on the passive Perception of the crew member in the crow’s nest or on lookout, with a failure allowing the warship to remain undetected and sail in closer than 1 mile before being noticed.

Scenario 2: Kraken At Tack

The adventuring party is traveling in their sailing ship when they see a lightning strike about 100 feet in front of their ship. A kraken hatching emerges 50 feet off their bow. Another lightning strike, and a kraken hatching emerges 50 feet off their stern.

Setting: Sunny skies with strong wind blowing north (+15 ft.) over clear, shallow seas with many shipwrecks underneath. Let’s start with piloting in these condition at DC 10 (to avoid some jagged rocks) and visibility is 5 miles.

Range: The krakens emerge 50 feet off the bow and stern. Everyone is close enough to cast a spell or make a ranged attack. The krakens will maintain this distance (or less), traveling with the boat until they disengage or are defeated.

NPC Intention: Two kraken hatchlings are learning to hunt. The krakens are hostile and want to sink the ship and/or eat the crew. Their adult kraken mother is unconcerned and watching, hidden below.

Player Intention: The players decide they will fight and continue to sail north and try to escape the territory of the kraken.

Speed: The ship’s velocity is 45 feet per round (30 ft. + 15 ft. wind). The kraken hatchlings have a speed of 50 feet and can easily keep up with the ship.

Initiative: Roll initiative, since the first lightning bolt puts the crew on alert and the kraken is hostile.

How I ran this encounter: With a crew manning the 3 cannons and 2 swivel guns, my 10th level players made easy work of the kraken hatchlings and their kraken mother. Their ship continued to sail north. The krakens left them alone once they escaped the territory, which I set to be 10 rounds (450 ft. of travel), or until the krakens were hurt enough to withdraw. The sorcerer casting banishment during this fight is something my players still talk about.