Like skydivers, mountain climbers and surfers, scuba divers often crave a challenge. It’s a beautiful thing about the sport — you can keep it tame, or you can stretch the boundaries. Are you itching to survey the interior of a shipwreck? To venture beyond the reach of the sun and into a cave system? Step outside the cage and dive with great white sharks? Discover an unexplored underwater wilderness? With the right gear, training and mindset, you can do just that. Around the globe, these are the destinations where expanding your limits pays off with unforgettable, one-of-a-kind experiences.

USS Oriskany
Pensacola, Florida
The Mighty O hails as the largest artificial reef in the world — and one of only a few aircraft carriers welcoming underwater visitors. Recreational divers are largely limited to exploring the bridge, which starts at a depth of 80 feet, but can also enjoy views of the flight deck at 145 feet — which, for tec divers, is only the beginning.

Peleliu Express
Palau
Ride the incoming or outgoing tide — sometimes as strong as 4 knots — as it makes its way past Peleliu Island, bringing with it a host of pelagic life, including some 20 to 50 gray sharks, plus the odd blue marlin and even whale shark. Visibility is excellent, upward of 100 feet, compromised only by the curtains of schooling oriental sweetlips, palette surgeonfish and rainbow runners.

Cenote Car Wash
Tulum, Mexico
Filled with light, the beginning stretches of this easy-access cavern are well-suited to divers of all abilities who wish to see stalagmites — including a room of soda-straw-like formations — as well as lily pads, downed trees and gnarled tree roots, along with the freshwater fish swimming among them.

Darwin’s Arch
Galapagos Islands, Ecuador
This stone arch sits atop an underwater plateau known as the Theater, which serves as a viewing grounds for the hundreds and even thousands of schooling scalloped hammerheads and jacks that collect at this island — which, paired with Wolf, sits 115 miles from the next outpost of land.

USCGC Spar
North Carolina
Sand tiger sharks are the most charismatic regulars at this 180-foot buoy tender off the coast of Morehead City, North Carolina, sitting upright in 110 feet of water. The slow-moving, pointy-nosed predators circle the top deck and the perimeter of the ship where it meets the sand, giving photographers ample angles for exquisite shots.

Secret Bay
Anilao, Philippines
The secret lies in the muck. Or rather, countless secrets: This 60-foot-deep wonderland of weird is home to a long list of the small, odd stuff, including the blue-ringed octopus, the wonderpus octopus, ghost pipefish and the bobbit worm.

READ MORE: The 10 Most Accessible Dive Sites in the World

Roca Partida
Socorro Islands, Mexico
The smallest of the Socorro Islands, this volcanic outpost is one of the world’s biggest gathering spots for giant mantas, which boast wingspans up to 22 feet. This site is also a hot spot for 10 species of shark, including giant hammerheads, whitetip reef sharks and scalloped hammerheads.

Race Rocks
British Columbia, Canada
Fast currents rush past this rocky inlet, but if you time it right, you can linger at this wall covered in strawberry anemones, white plumrose anemones and more. California and Steller sea lions are seen on most dives, and on occasion, killer whales are also observed.

Switzer
Solomon Islands
Named for Switzerland, home of the Alps, this site and its underwater mountains give divers a drift experience over sheer slopes covered in anemones, hard coral and the animals that call them home.

Scapa Flow Wrecks
Orkney Islands, Scotland
The British weren’t successful in stopping the Germans from scuttling several ships — three battleships, three light cruisers and a minelayer — following news of World War I’s outcome. The 388-foot SMS Dresden, one of the light cruisers, is a highlight thanks to its depth of 82 feet, shallow compared to the rest of the sunken fleet, and the fact that it remains fairly intact. Also popular is the 510-foot SMS Coln, the most intact of the cruisers, still armed with most of its guns.