underwater caves(water worm and heat vents)

I believe that while Minecraft has added scary things to the underground world with the warden the new creaking for above that the water needs something to. which is why i would like to add the water worm to under water caves as they are currently empty. they would be large wormlike creatures that would hide deep in the narrow under water caves seeking for food. they would mainly live in the new heat vent block. however the player needs a reason to venture in to this dangerous area. which is why I think that in the area there should be more treasure hidden deep in the caverns. also i would like this mob to be similar to the warden in the fact that it attacks anything in the caves and not just the player.by the way the name is a little weird so if you think of a better name please do that instead.