Could anyone help with resolving the tagging here, so that the water areas become the inner part of a multipolygon and don't show up as fen, but as water (even though they're part of the general fen area)? 

This is to indicate the water within the multipolygon is 100% water and doesn't have any land.

I tried a multipolygon, but rendering has gone rogue which I resolved with a quick fix... apologies if I made things more complicated. Is there a way to undo two entire changesets? 