Collision Groups with Terrain

I am trying to separate collision groups based on the type of terrain-- i want collision of a part with water, but i don’t want it to collide with land. I don’t see this available in the standard collision group editor, and before i move this to scripting (if its even scriptable), i thought i’d try here first since its a building issue.

I’ve also checked out this post, but its not relevant to my case where I want the terrain types to be distinguishable for collision:

Edit: to elaborate, the reason i want collision with water is it is boat related and helps the physics of the boat on water, so making it noncollide with all terrain would render it useless in the water.

Re-Edit: I’ve moved this over to scripting since no replies in Building.