Antarctic ice fish
The Antarctic ice fish resides in the Southern Ocean. 122 species are currently known; more continue to be described.
All species lack swim bladders. They are largely benthic, residing on the sea floor, though some species have evolved enhanced buoyancy through larger lipid deposits and lower bone density. Most species have some degree of antifreeze glycoprotein in their blood, aiding their survival in subfreezing temperatures. Some species inhabiting oxygen-rich waters have no hemoglobin in their blood, relying only on normal blood plasma circulation to transport oxygen to their tissues.
I enjoy the fact that the things look like flamboyant caiman-catfish hybrids.
Wikipedia link.
National Geographic link on their moving into new habitat after the Weddell Sea ice shelves collapsed.