Bathypterois grallator

Short answer: Bathypterois grallator, the tripod fish or tripod spiderfish, is a deep-sea fish in the family Ipnopidae. George Brown Goode and Tarleton Bean described it in 1886.

It lives on continental slopes and abyssal plains in the Atlantic, Pacific and Indian oceans, roughly between 40°N and 40°S, at depths of 878 to 4,720 m and water temperatures of 2.7 to 13.5 °C. It's the largest member of its genus, commonly over 30 cm long and up to about 43 cm. The lower lobe of its tail fin and both pelvic fins end in greatly elongated rays, up to about a meter long, or roughly three times its body length. When it settles, it lands on its pelvic fins first and then lowers its tail ray, standing on the three like a tripod. The rays are flexible when it swims but stiff when it stands, and researchers have suggested that the fish pumps fluid into them to stiffen them. Standing facing into the current, it waits for food to drift past and uses the tips of its pectoral fins to feel for prey, since its eyesight is very poor. Small tripod fish eat mostly copepods, amphipods and other small crustaceans. Larger ones, above about 24 cm, eat mostly small fish and decapods by weight. Each fish is a simultaneous hermaphrodite and may be able to fertilize its own eggs, which helps where mates are scarce. The IUCN lists it as Least Concern. The footage, credited to the Schmidt Ocean Institute, shows a pale tripod fish drifting and standing on long fin rays over a dark, sandy seafloor.