underwater forts?

[LintMan]

Newbie question here: is there any way to build forts under water?

I marched my Jotunheim pretender underwater, claimed a few water provinces, and built some native water troops, but the only thing I'm able to build is a lab. Even the native underwater commanders can't build forts.

Is there no way to get the fort's supply and production bonuses underwater?

Also: can you build temples underwater? I haven't found any native underwater priests yet, and I didn't bring a land based one with me.

Thanks!