After seeing the trailer for the film Survive (2024), I have to wonder: is this a parody and the trailer just didn't convey that well enough?
Water doesn't work like that. Land masses and seas don't work like that. We're not supposed to take that seriously, are we?
The premise is intriguing. It's really the same as the Lovecraft story Dagon initially. But you'd have to either leave it unexplained or give a vaguely believable explanation. It doesn't even need to be more convincing than The Core. But having it remain unexplained might be the best option.
And worst of all: they have to deal with large deep ocean crabs, not with isopods! If this were a giant isopods film, I might try to ignore the physics of it in order to watch it. But not for crabs.