I think theres specific code to keep animals out of water, it doesn't always work so a mod taking advantage of that flaw in the code would probably work if you can code and have the source code ! LOL ! Anyway that's the end of that ! I know of no way to spawn animals under water or POIs reliably for that matter. The game has been designed so things Don't spawn under water so good luck trying to find a way around it that doesn't bug out on you but it doesn't seem possible.
Water in the game isn't even working right yet. They still need a lot of work to get it to flow and fill voids and such.
Has anyone tried a fixed POI setup with one POI manually set into water? Haven't tested myself, must admit that.
When I owned a boat, I discovered to my dismay, that a boat is a hole in the water you toss large sums of money into you never want see again.
That's part of it, yes. The game will fill in any closed building below sea level with dirt. If the building isn't closed, like say it has 3 walls and no roof... there will be a square hole in the water. The water isn't dynamic yet.