Blobfish and snailfish
Blobfish (Psychrolutes species) don’t need muscles – they have a feeding strategy that consists of sitting and waiting for something edible to go by. As well as that, their jelly-like flesh is slightly lighter than water, so they don’t need to expend energy or scarce oxygen to stop themselves from sinking towards the sea floor. This low-density flesh is an alternative to a gas-filled swim bladder, a feature of many fish in less deep waters. However, at 800 metres deep the pressure is about 80 times higher than at sea level, so any gas would be too compressed to serve the purpose. Also in this photograph is a small red snailfish, another deep-water species with a jelly-like layer.
http://www.teara.govt.nz/en/deep-sea-creatures/2/2
