Dive into the Video Gallery! The ghost-white hydrothermal vent crab is a top predator at vent sites. When this crab is very young, it is bright red and less than an inch long. The adult may reach a maximum size of about 5 inches. The white, snake-like zoarcid, or eelpout, is the most common fish seen at hydrothermal vent sites. Hair-like projections ("cirri") line the webbed arms of this deep-sea octopus. These projections may help it sense food in the darkness. This species also is equipped with paddle-like fins to help it swim. Pompeii worms stick their dark-red feathery heads out of their tube homes. This worm is the hottest known animal on Earth. It can withstand temperatures as hot as 80°C (176°F).