A two and a half foot sea isopod:
They may look frightening, but they're actually quite charming. Well, maybe not, but they do seem to eat only dead or very slowly-moving prey:
Although generalist scavengers, these isopods are mostly carnivorous and feed on dead whales, fish, and squid; they may also be active predators of slow-moving prey such as sea cucumbers, sponges, radiolarians, nematodes, and other zoobenthos, and perhaps even live fish. They are known to attack trawl catches. As food is scarce in the deep ocean biome, giant isopods must make do with what fortune brings; they are adapted to long periods of famine and have been known to survive over eight weeks without food in the aquariums of irresponsible owners. When a significant source of food is encountered, giant isopods gorge themselves to the point of compromising their locomotive ability.
So go ahead and hit that deep-sea dive! Just keep swimming quickly.