“Now, had we shot on the tank I don’t think Jaws would have been very successful, because it would look really phony. So I really insisted on the sea, but innumerable problems… physical problems, came along with my decision. One of the first things we had to do was find a open sea where you couldn’t see land, and where there was a 30 foot flat, sandy bottom so the shark sled would have some place to [stand]… It had to be 30 feet because if it was 40 feet, the shark could never get out of the water. We had a shark arm that only went up so high. The problem about shooting in the shallows 10 to 12 miles out to sea is that the shallows pile on the waves. You don’t get breaking waves out there, but you get some swell out there because of the shallowness. So we picked the worst place in the world to shoot.”
Spielberg talks to Entertainment Weekly about the difficulties of shooting Jaws at sea.