If a vehicle has a suitable shape and enough speed, it will stay above the surface with just the hydrodynamic lift on the surfaces. So planing hulls, hydrofoils and such should work as long as you keep it moving fast enough.
I tried to hydro-plane the d15 with 3x wider wheels across the water on gridmap at 80mph and sadly did not make it far edit: not to disagree I just felt like commenting
The default wheels have no effect in water. A custom wheel with paddles made of submesh triangles, powered by rotators, should work. Propellers built like that work very well.
haha that's why it sank in the same spot every time then. I'll have to try that out sometime. with rotators, would it be possible to make modified wheels like the ones on the firebug crawler without editing any lua files?