Pressure Capsule
Wondrous Item, common
This small capsule is made of beeswax blended with sand and a variety of enchanted water plants. A creature who consumes a pressure capsule ignores the effects of swimming at depths greater than 100 feet (see ""Unusual Environments"" in chapter 5 of the Dungeon Master’s Guide).
Source: Ghosts of Saltmarsh p. 229