So Tanya Streeter broke the world free diving record after plummeting to a depth of 525 feet. How is this possible?

Submarine crews, when they have to escape, use a special chamber and diving equipment and are warned to rise slowly, otherwise they will develop the bends and have to go into a decompression chamber when they surface.

How can a girl descend 525 feet in a minute-and-a-half and return in the same time?

-Cyril Noyce, Roundway, Coldean