Very entertaining post! It reminded me of a few Youtube videos about the kind of wildlife you encounter as you go down into the sea, even to the deepest depths.

I also remember watching a documentary that some of these deep sea animals are mostly scavengers. They feed on the carcasses of sinking animals, notably whales, which can last a long time, providing a long-lasting ecosystem down there.

BTW, on this part:

Their anatomy must be adapted to withstand very high pressures and temperatures between 0 degrees or less

It left me a bit puzzled, as I am learning that sea water has a freezing point below zero degrees Celsius. Is that what you meant?