PHILADELPHIA (CBS/CNN) — New Jersey native and former NASA astronaut Kathy Sullivan is making history and an incredible splash. 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: Sullivan.

On Sunday, Sullivan visited Challenger Deep, a location in the Pacific Ocean’s Mariana Trench. It is nearly 35,000 feet below the surface.

Sullivan is also the first woman to complete the dive in a special submarine created specifically for the trip.

Credit: CBS3

About 200 miles from the trench, Guam is the nearest land mass.

Sullivan is the first of the three explorers to finish the roughly 10-hour mission, with two more to follow this week.

“I know (Challenger Deep) as a bathymetric feature on a chart, a tectonic feature, and a seismic feature … but that’s all data-based understanding. To see it in person — it makes all the difference in the world,” Sullivan tells CNN Travel.

“No self-respecting marine biologist would be able to pass up an invitation!” she said.

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