Its an aviation clich that your single engine goes into automatic rough when crossing any significant body of water. To be sure, any engine problem while beyond gliding distance from land is a critical problem, even if you have more than one. When flying a single, its everything. Another clich is that most of us dont bother to analyze the real risks of overwater flying. Any water crossing of any significance-and wed put the Great Lakes, Hawaii and Bahamas in that basket-should be carefully planned to ensure risks are mitigated to acceptable levels. The thing is, both clichs are true more often than not.