A rare photo of a Big-Fin Squid, caught on camera on November 11th 2007 by a Shell Oil company ROV, at a depth of 2,386 meters (1.5 miles). This species of Squid dwell at extreme depths, and are characterised by their long, thin tentacles. They can reach almost 20ft long when fully grown.
Hasan Jasim
ROV video:
Of course, much of our knowledge about deepwater biology is attributable to oil and gas exploration and the associated environmental studies. This includes the discovery and study of chemosynthetic communities in the Gulf of Mexico:
Some of the same conditions responsible for petroleum deposits also provide the basis for biological communities that receive energy from chemicals through a process called chemosynthesis (in contrast to photosynthesis that provides energy to terrestrial and shallow-water communities through processes in which sunlight is the basic energy source).
NOAA
Bud's Offshore Energy (BOE) 