Ed Harris did not actually breathe the fluid. He held his breath inside a helmet full of liquid while being towed 30 feet (10 m) below the surface of the large tank. He recalled that the worst moments were being towed with fluid rushing up his nose and his eyes swelling up. Actors played their scenes at 33 feet (11 m), too shallow a depth for them to need decompression, and rarely stayed down for more than an hour at a time. Cameron and the 26-person underwater diving crew sank to 50 feet (17 m) and stayed down for five hours at a time. To avoid decompression sickness, they would have to hang from hoses halfway up the tank for as long as two hours, breathing pure oxygen.