I bought S&Box and started messing around with the editor. It’s pretty much unity (which I’m pretty sure the game started on unity so I wouldn’t be surprised if a bunch of it is ported monodevelop stuff.

Anyways I made a boat and made it float in game:

The physics to do this might be there internally but instead of looking for that, I ended up just making an ocean component that I tied to a trigger box. Might keep poking at it, just because S&box has the annoying multiplayer part sorted already.