Salem

Don't know if this has been suggested, but if I pour enough dirt into shallow water it should become land.

and then become water again

Nah I mean to be able to build on.

Yes, you are right, it has been suggested before, did you do a search?

Yes, please search on these sorts of things. The idea has been posted before and the devs have already stated that it's not coming right now. It's just not doable within the current game design. (paraphrase--the specific statement is around here somewhere on water terraforming)