Flying over large bodies of water should never be taken lightly, a friend of mine who flies regularly over the Great Lakes uses the following criteria as a go no go.
He does not attempt to fly across the lake unless he is at an altitude where by should his engine/s quit he can safely glide to one shore or the other. If he can't reach the altitude that he determined is safe, he turns around and goes home.
Often in a Cessna Caravan (C208) this means he must be at 8000 or higher, depending on weather conditions. One must never forget that even in the heat of an August summer that the water temp out near the middle of the Lake Michigan rarely exceeds 60, Lake Superior is even colder. If you go for a swim how long can you tread water before hypothermia sets in? How long does it take Seach and Rescue to launch and find you?
It never ceases to amaze me to see pilots flying VFR or IFR over long distances of water down low where should their engine quit they are guaranteed that they are going for a swim.
Granted todays aircraft engines are extremely reliable, but why risk becoming a statistic?
Mike
NATCA FWA