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Recreational scuba divers' recommended maximum depth is 120 feet. Usually we go 60-70 feet and see great sights. My maximum depth was one carefully planned and executed dive to 134 feet to see a spectacular underwater sea mount in Saba Marine Park in the Caribbean. In some parts of the Caribbean, you can dive maybe 80 feet and look over the edge of the ocean shelf into the abyss - endless dark depths. How puny is man on this planet - that we have seen so little of the ocean depths. We only "explore" it enough to get at oil or indiscriminately harvest fish - with little regard for the destruction or devastation we wreak.
From Wikipedia, the free encyclopedia
A bathyscaphe (play /ˈbæθɨskeɪf/ or /ˈbæθɨskæf/) is a free-diving self-propelled deep-sea submersible, consisting of a crew cabin similar to a bathysphere, but suspended below a float rather than from a surface cable, as in the classic bathysphere design.
The float is filled with gasoline because this is readily available, buoyant, and for all practical purposes, incompressible. The incompressibility of the gasoline means the tanks can be very lightly constructed as the pressure inside and outside of the tanks equalises and they are not required to withstand any pressure differential at all. By contrast the crew cabin must withstand a huge pressure differential and is massively built. Buoyancy can be trimmed easily by replacing gasoline with water, which is denser.
Mode of operation - To descend, a bathyscaphe floods air tanks with sea water, but unlike a submarine the water in the flooded tanks cannot be displaced with compressed air to ascend, because the water pressures at the depths for which the craft was designed to operate are too great. For example, the pressure at the bottom of the Challenger Deep is more than seven times that in a standard "H-type" compressed gas cylinder. Instead, ballast in the form of iron shot is released to ascend, the shot being lost to the ocean floor. The iron shot containers are in the form of one or more hoppers which are open at the bottom throughout the dive, the iron shot being held in place by an electromagnet at the neck. This is a fail-safe device as it requires no power to ascend; in fact, in the event of a power failure, shot runs out by gravity and ascent is automatic.
In 1960 Trieste, carrying Piccard's son Jacques Piccard and Lt. Don Walsh, reached the deepest known point on the Earth's surface, the Challenger Deep, in the Mariana Trench. As of 2010, these two remain the only people to reach this extreme depth. No manned vessel has ever repeated this feat. In 1995, the Japanese sent an unmanned submersible to this depth, Kaikō, but it was later lost at sea. Most recently, in 2009, a team from the Woods Hole Oceanographic Institution sent a robotic submarine named Nereus to the bottom of the trench.
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