330-PSA-23-65 (USN 1108798):  Project Sealab II is scheduled for late next summer when an underwater residence will be established 250 feet beneath the Pacific, one mile off La Jolla, California.  Two ten-man diving teams will live in the undersea laboratory for periods of 15 to 30 days.  Sealab II, shown here in an artist’s conception, will be a cylindrical structure 50 by 12 feet, designed to provide easy access to the sea.  Atmospheric pressure within the lab will be 100 pounds per square inch, the same pressure as that of the sea at 250 feet.  As in Sealab I, conducted 30 miles off Bermuda last July, the major objective of Sealab II will be to determine how much useful work can be accomplished by divers in an ocean environment at great depths.  The divers will breathe a specially formulated gas mixture consisting of Helium, Oxygen and Nitrogen, with Helium the major component.  Sealab II will be self-sufficient with respect to food, water, and breathing the gas mixture for at least six weeks.  Photograph released February 5, 1965.  (2015/11/10).
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/127906254@N06">National Museum of the U.S. Navy</a>
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