On January 23, 1960, the Swiss oceanographer Jacques Piccard, son of the bathyscaphe's inventor Auguste Piccard, and US Navy lieutenant Don Walsh, took the bathyscaphe Trieste to the bottom of the Mariana Trench in the Pacific Ocean, 35,797 feet down.
The Solar Impulse, home of son and explorer Bertrand Piccard, describes the trip:
At 1 pm, after a four and a half hour descent into the trench, the two men reached a depth of 11,521 metres according to their instruments - later revised to 10,916 metres - in keeping with the water's density and temperature. After reaching the two Poles and climbing Everest, this meant that the "fourth corner" of the Earth had now been conquered. Eleven kilometres under water is equivalent, going the other way, to the altitude at which planes on intercontinental routes now fly.
At this depth never reached by sunlight and where the pressure is 1,000 times greater than on the Earth's surface (1091 atmospheres or 1.1 tonne per cm2!), one would think that nothing would be able to live. Yet the two men were completely surprised to see, in the light of their arc-lights, several shrimps and even a real 30cm deep-sea fish resembling a sole. Resurfacing at 6 pm, they had managed to prove the existence of vertical currents circulating oxygen between the surface and depths, making life possible at such depths and at the same time putting an end to any ideas about storing radioactive materials and other waste in the trenches - the birth of modern-day ecology.
They were on the bottom for all of twenty minutes.
The trieste was a simple, clever design; the two men were in the pressure vessel at the bottom, while the function of the rest of the ship was to be bouyant enough to float them back up. But the flotation tanks had to be filled with an incompressible liquid, so they filled it with gasoline. Nine tons of iron pellets of ballast gave them enough weight to sink; they dropped it at the bottom and rose back up. Wikipedia