Skin-diver King

h#3

Skin-diver black King

1. Kh5, Bf2 2. Bh6, g4 + 3. K underwater, Kf5 #

* When a King is checked, it may plunge "underwater" (i.e. under the surface of the chessboard), but, in this case, it must re-emerge with the next move. If the emersion is impossible, the King is mated (it drowns)