Not good.
http://joxi.ru/MAjbpq9hj4WygA
Are you using the same particle shader for all 3 simulators? If so, each particle shader can pick just a single simulator node, so the particle won’t know if they are underwater or not. So you gotta use 3 particles shaders, each pointing to a different simulator.
Hm. You merge grids, but don’t merge particle shaders. I thought, it was logical, to use master grid, as an underwater guide too (like for ocean material). I’m worried, if there will be created 50grids. For now shader can only use one grid, as a liquid simulator.
P.S. No nightlies for maya 2018 win, since nov8.