Ring of the Dolphin 2014
Ring, uncommon, (requires attunement)
This gold ring bears a jade carving in the shape of a leaping dolphin. While wearing this ring, you have a swimming speed of 40 feet. In addition, you can hold your breath for twice as long while underwater.
Source: Vault of Magic (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details