The depth a human can go underwater depends entirely on the equipment and technology being used. A recreational scuba diver is generally limited to 40 meters (130 feet) due to the risks of nitrogen narcosis and decompression sickness. Commercial "saturation" divers, who breathe specialized gas mixtures (heliox), can work at depths of 200 to 300 meters (approx. 1,000 feet). The world record for a deep dive in a specialized scuba suit is roughly 332 meters. Beyond these depths, the human body cannot withstand the immense pressure of the water without a hard-shell protective barrier. In a Deep Submergence Vehicle (DSV) like the famous Alvin or James Cameron's Deepsea Challenger, humans have reached the very bottom of the ocean at the Challenger Deep in the Mariana Trench, which is approximately 10,935 meters (35,876 feet) deep. At this depth, the pressure is over 1,000 times atmospheric pressure—equivalent to having an elephant stand on your thumb.