Your boat is leaking water. http://www.youtube.com/watch?v=eRC9FDin5dA&t=1m13s
This can be easily avoided using depthmasking. DepthMask - Unify Community Wiki
In order to get that working, control over the render queue is needed, which can currently achieved using a custom comparator and checking userdata. Other engines (unity, openscenegraph) have an integer built in for that. Nonetheless, since it’s working, I’m not going to request such an integer. Instead I will ask how you plan to support such things in the sdk? Are you planning on making custom geometry comparators selectable?
Has nothing to do with the SDK. Whatever way this will be solved in the engine one can adapt that solution in an SDK window. E.g. via an AppState and/or special Controls.