Humans can build in water, they can also dive. The game limitations on building are frustrating, not fun. Thankfully we have modders who are also frustrated with it. The only way to truly build things is with mods and dev commands... and that's bad game design.
I'm not asking to be able to build in the ocean biome 300m down, I just want better snapping and the ability to use tools in the water like humans can. I also want to build ALL of the things you can find in the game, so frustrating finding a dverger camp/fuling camp, etc and not being able to build any of the things they have. I hate that part of crafting base building games "you can't build this, it's race exclusive..."