Credit: Photograph by Jimmy Chin

At the narrow entrance to the Persian Gulf, the jagged limestone walls of the Musandam Peninsula, in Oman, form a deepwater soloing oasis. Rock climber Alex Honnold – the only person ever to free-climb Yosemite's three biggest walls in one day – and world-class adventure photographer Jimmy Chin toured the coast's fjord-like waterways on a 45-foot catamaran, taking day trips by Zodiac to the sun-baked rock formations that rise out of 80-degree seawater.

"I'm sure we did more than 10 first ascents," says Chin, of the three weeks they spent exploring the coastline. "We climbed a spire that had to be 700 feet," says Honnold. "You could see schools of tuna jumping in the distance, flying fish skirting the surface – I even saw a sea turtle as big as a man." Climbing horizontally on deteriorating overhangs, though, made for some harrowing moments.

"Your feet could hit the bottom of the ocean if it wasn't high tide," Honnold says. At one point, he narrowly avoided an encounter with a venomous lionfish: "It was just lurking there beneath me." During one early morning scramble, he stumbled upon a plateau littered with 500-year-old ruins. "It felt like I had discovered an ancient civilization," he says.