Size:16 ft. long, 4.5 ft wide, 4 ft. high Weight: 5,000 lbs. Operating Time:8 hrs. Crew:One- and two-person configurations Max Depth: Initially 6,500 ft., eventually 35,800 ft. Vertical Speed: 500 ft./min. ascent, 400 ft./min. descent. Nick Kaloterakis
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Surface

The weight of air exerts an imperceptible 14.7 pounds per square inch (psi) in all directions

33 Feet

Exactly double the pressure at sea level. Even with a snorkel that reached the surface, the pressure on your body is too great to take a breath.

500 Feet

Even with scuba gear, this is where most divers start to experience high-pressure neurological syndrome, which causes headache, tremors and muscle twitching. Nerves can’t adapt to the increased pressure and malfunction.

702 Feet

The free-dive record (no scuba gear), set by Austrian diver Herbert Nitsch in 2007. At this depth, his lungs were almost 95 percent collapsed and the rest filled with blood plasma.

1,044 Feet

The depth at which South African diver Nuno Gomes set the scuba-dive record in 2005. Gomes was convulsing so badly that the respirator was coming loose from his mouth.

1,500 Feet

Specific depths are classified, but nuclear attack subs typically operate in this territory.

6,500 Feet

Target depth for one of three versions of Deep Flight II Graham Hawkes hopes to sell. He also plans to offer a model that will reach 22,000 feet, and another capable of full-ocean depth.

12,500 Feet

Resting place of the RMS Titanic, which sunk in 1912

21,000 Feet

Target maximum depth for the new Alvin, after final upgrades in 2015

35,800 Feet

At this depth, the pressure is more than 1,100 times that of the surface, or over 15,000 psi. Only two people have ever reached this depth, in 1960 in the Trieste. The window began to crack, so the record-setting trip was cut short after just 30 minutes on the bottom.

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