Just wondering if there is a pluggin or a setting that allows me to build in the deep ocean! Thanks for any help!

(Deep ocean as in the ocean waaaaay out there where you cant see land anymore. To the point where it despawns your boat when you get to far and there is a noticable line on the ocean floor)

On water level on deeper?

The problem you will find is that even when wearing diving gear you have to make sure you have a lot of tanks as there is no visual indication of how much air you have left, The game devs should have "swapped" a health/food/water bar for one showing air when they introduced the diving , I have built 4 floors deep but it is tricky and you have the stability problem of your levels above the water, You cannot place a TC in water (even very shallow) so that would have to be placed above the water line.

Deep as in when you get in a boat and just go away from land for like 5 minutes. You get so far from land that your boat gets despawned and you are then like 2 hours away from land swimming. 

You can only build in the ocean on the ocean floor that has seaweed. The bare dirt that is past the seaweed dirt blocks you from building. We need to be able to build on the bare dirt.

Why ?

I used server.stability 0 to build way out into the no build zone and I found something weird. When ever I place anything from a sleeping back to a tc or a chest it becomes invisible instantly. 

this is a rust issue if u build near the boundary it will get invisible yes. TC, boxes, some deploys :/
sometimes u see it and mostly after Server restart it will get invisible