What adaptations do fish need in order to survive in the deep waters?

Question

ive googled it but cant seem to find too much on it

Answer 1

Good vision, air bladder maybe to survive the bends, the ability to tolerate cold temperatures.

Answer 2

good vision (or no vision at all!), the ability to survive frigid temperatures, and most definitely the ability to withstand extreme pressure!  Many strata of deep ocean are relatively devoid of nutrients, so a way to attract food or find odd sources of food is very helpful as well.  The deep sea angler fish has a growth out of it's forehead that is luminescent.  It glows and attracts the fish's prey.