Descending to remarkable depths below the sea on one single breath, Alessia Zecchini enters what she describes as the last quiet place on Earth. The Italian champion is determined to set a new world record in freediving, a dangerous extreme sport in which competitors attempt to reach the greatest depth without the use of scuba gear. Freedivers are often subject to blackouts upon ascent, necessitating the help of safety divers like Stephen Keenan, a free-spirited Irish adventurer who fell in love with the sport in Dahab, Egypt. Having formed a special bond on the freediving circuit, Alessia and Stephen train together so she can make an attempt on Dahab's legendary Blue Hole and its challenging 85-foot-long tunnel 184 feet below the Red Sea. Their fates are inextricably bound together by a tragic event that ensues.—sundance