 From the first water test onward, the "non-absorbent" neoprene foam that made up the sharks' skin soaked up liquid, causing the sharks to balloon, and the sea-sled model frequently got entangled among forests of seaweed.Spielberg later calculated that during the 12-hour daily work schedule, on average only four hours were actually spent filming.Gottlieb was nearly decapitated by the boat's propellers, and Dreyfuss was almost imprisoned in the steel cage.