Cameron's cinematographer, Mikael Salomon, used three cameras in watertight housings that were specially designed. Another special housing was designed for scenes that went from above-water dialogue to below-water dialogue. The filmmakers had to figure out how to keep the water clear enough to shoot and dark enough to look realistic at 2,000 feet (700 m), which was achieved by floating a thick layer of plastic beads in the water and covering the top of the tank with an enormous tarpaulin. Cameron wanted to see the actors' faces and hear their dialogue, and thus hired Western Space and Marine to engineer helmets which would remain optically clear underwater and installed state-of-the-art aircraft quality microphones into each helmet. Safety conditions were also a major factor with the installation of a decompression chamber on site, along with a diving bell and a safety diver for each actor.