The Island — Peter Benchley

Two men and a boy, on the boat they charter to game-fishermen, are lazing away the hottest hours of a Caribbean day when they notice a cameo which appears to be adrift. They manoeuvre it alongside their boat, one of the men reaches to pull back the tarpaulin which conceals whatever it contains -- and the reader receives a jolting shock which reminds him of those famous first pages of Jaws.