All good advice from many. Personally I don't have an issue with flying over water in a single because like has already been said in terms of surviving the ditching the stats are on one's side. With a suit and raft (which is what I carry in the winter) if one gets a radio message out with position I feel confident a ditching should turn out OK. The aircraft has an ELT (although a PLB is probably better for water use) and there are some flares in the life raft pack.
Single door aircraft make me rather nervous though I have to say...