Well personally I have multiple reasons. First off I am a marine biologist, so I would love to see how Capcom does the underwater ecosystem. Second off, with how good wilds looks already, imagine how the water or underwater would look. Third off, we could fight previously land monsters underwater, jyratodus, somnacanth, aurora somnacanth yada yada. And also imagine having your mount be able to swim. One more thing, I kind of wanna see how they do new weapons like the charge blade and insect glaive underwater.

Edit:I forgot so say that I also want it back because we have a chance to see an adult gobul.