Just eight people have reached Challenger Deep, the deepest point of the ocean. More than 550 people have visited space.
But only one person has done both: Kathy Sullivan.
On Sunday, the NASA astronaut and oceanographer visited Challenger Deep, which sits at a depth of 10,928 meters (35,853 feet) in the western Pacific Ocean, as part of the Ring of Fire Expedition organized by bespoke adventure company EYOS Expeditions and undersea technology specialist Caladan Oceanic.
Read more at CNN Travel.