Brine Claw

Weapon (dagger), unique (requires attunement by a barbarian, druid, or ranger)

This +1 dagger has no hand guard. The hilt is a scrimshaw whale bone depicting creatures of the deep; the blade is a single tapered, sharpened edge that forever smells of the sea.

Radiates: Abjuration and conjuration magic.

Power: You are never seasick and gain advantage on all Dexterity checks and saving throws made over, in, or underwater (so on bridges, docks, ships, etc.).

Power: You gain advantage on swim-related checks.

Power: You deal an extra 1d6 necrotic damage with this weapon as it injects bacteria-contaminated salt water into the wound. In addition, the creature struck must succeed on a DC 10 Constitution saving throw or become poisoned for 1 minute.