As you can see in the screenshots, I just added highly accurate hydrostatic/hydrodynamic physics in Rigs of Rods.
In the same philosophy that makes RoR so different, this is not just an approximated Archimedes law that was added, but a realtime local pressure gradient computation, that is able to accurately simulate any buoyant shape, in any position, and even with uneven water surface (waves!).
With this method, making boats is also quite easy, you just have to mark cab triangles as part of the hull and that's all! The water pressure gradient will be applied to the "wet" side of the triangles, and all these pressure forces will combine to make the boat float.
As always, the physics (the fun part!) is only 10% of the code, and I have yet to integrate boats to the gameplay (making nice dashboard, sounds, special effects, port infrastructure...).
A small video: