Bladderfish

The Airsack (in early builds called the Bladderfish) is a life form belonging to the fauna category.

It is catchable, harvestable and can be eaten raw. They are most found in the Safe Shallows biome. They stand out in comparison to other small fish, as they can be used to craft filtered water, which fills up 20 H2O. As a result, Airsacks are the second best source of H2O, after disinfected water. When in Freedom mode, you can click on it to replenish your oxygen.

Its speed is rather low and its attitude is passive, making it easy to catch. It is especially easy to catch during nighttime, when they are next to immobile due to their diurnal (dayactive) properties.

Appearance
The Airsack is a small fish that is comprised of a long, extremely thin main body with large transparent air bladders on the top and bottom. These bladders have slim blue spines extending up from their outer edges, and they throb and undulate as the Airsack moves. The Airsack's head is bright orange and ovular in shape, possessing no discernible mouth and a pair of large eyes. Its bladders also appear to have a dull bioluminescent glow.