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. The cast and crew endured over six months of grueling six-day, 70-hour weeks on an isolated set. At one point, Mary Elizabeth Mastrantonio had a physical and emotional breakdown on the set and on another occasion, Ed Harris burst into spontaneous sobbing while driving home. Cameron himself admitted, "I knew this was going to be a hard shoot, but even I had no idea just how hard. I don't ever want to go through this again". For example, for the scene where portions of the rig are flooded with water, he realized that he initially did not know how to minimize the sequence's inherent danger. It took him more than four hours to set up the shot safely. Actor Leo Burmester said, "Shooting The Abyss has been the hardest thing I've ever done. Jim Cameron is the type of director who pushes you to the edge, but he doesn't make you do anything he wouldn't do himself." A lightning storm caused a 200-foot (65 m) tear in the black tarpaulin covering the main tank. Repairing it would have taken too much time, so the production began shooting at night. In addition, blooming algae often reduced visibility to 20 feet (6 m) within hours. Over-chlorination led to divers' skin burning and exposed hair being stripped off or turning white. As production went on, the slow pace and daily mental and physical strain of filming began to wear on the cast and crew. Mary Elizabeth Mastrantonio remembered, "We never started and finished any one scene in any one day". At one point, Cameron told the actors to relieve themselves in their wetsuits to save time between takes.