Underwater mountain

As underwater mountain enters the battlefield,
you and target opponent have a heated argument
about if underwater mountain is a mountain or
an island. if you win the argument, it enters as
the basic land type that you argued for, if you
lose it becomes the basic land type the other
player argued for. if the argument remains
unresolved for long enough that a slow play
warning can be issued, instead it becomes
both and enters the battlefield tapped.