Has anyone tried Prepar3D in the underwater mode I believe it supports via Flyinside FSX? I don't have a copy of Prepar3D myself, but I would be interested if someone fancies trying out the Gerry Anderson "Supercar" craft and see if it goes underwater or if it needs any config/.ini file adjustments to do so? Post an image if it works too will you?
http://blog.inf.ed.ac.uk/atate/2016/01/13/fsx-supercar-at-knight-inlet-bc/