On August 25th, 1965 the first of three teams of "aquanauts" descended into the Pacific Ocean where their new home for the next fifteen days awaited. Affectionately referred to as the "Tiltin Hilton" due to the slope of the site at La Jolla Canyon off the coast of California, Sealab II was located at a depth of about 205'.
USN Captain George Bond, known as "Papa Topside", monitored the aquanauts and the experiments they carried out.
The aquanauts were aided by Tuffy, a bottlenose dolphin, from the US Navy Marine Mammal Program that shuttled supplies from the surface.
Astronaut Scott Carpenter stayed a record 30 days in Sealab II and even took a call from Astronaut Gordon Cooper who was in a Gemini space capsule orbiting the earth.
Sealab II was 57' long and 12' in diameter. The construction of the cylinder endbell was formed in an unusual way. The large dish-shaped cap was created from a sheet of one-inch thick flat steel placed over a die. One hundred pounds of C-4 explosives were evenly placed on the side of the blank opposite the die. The whole mass weighing about 60 tons was lowered 30' into the ocean where it was detonated. It took less than .004 seconds to form Sealabs II's endbell.
After Commander Carpenter's record 30 days saturation dive he received a congratulatory phone call from President Johnson. Due to the fact Commander Carpenter was still in a decompression chamber breathing a mixture of gas containing helium, his voice was altered. The audio above is a copy of the recording that circulated among Navy divers and was eventually aired on National Public Radio. Images and video are from US Navy archives and the Navy production film "Man In The Sea".