For decades, divers have been testing the limits -- of both themselves and their gear -- breaking out of their comfort zones, and exploring the underwater world and their relationship to it. While many divers are happy cruising shallow reefs, looking at the pretty marine life, well-lit by the sun's rays, and then casually breaking the surface and heading back to the dive boat, others find this experience monotonous. I mean, after you've done this a few times, aren't you ready to ratchet up the adrenaline a little? Maybe try some unusual, deep, or steep, wrecks; dive in frigid Antarctic waters; cruise past the stunning Eye of the Needle; or brave the Pacific's deep water currents, which are also filled with sharks? In the spirit of Brendan O'Brien's piece in Divernet, in which he recounts some "extreme dives," I thought I'd mention a few extreme dives, too.

• For many people, an "extreme" dive probably means diving very, very deep. Navy diver Daniel Jackson recently plunged to 2000 feet performing a solo test-run of the Navy's new Atmospheric Diving System suit. He compared the experience to witnessing a "star show."
• Freediver Guillame Nery recently finned down more than 350 feet on a single breath -- and then returned to the surface. Using no ropes or sleds (i.e., the Constant Weight Discipline ), the Frenchmen accomplished this amazing feat in just under three minutes.
• If diving deep isn't extreme enough for you, maybe Louise Trewavas's stunt will get your blood pumping. Hauling a shirt and an ironing board down to more than 450 feet off Dahab, Egypt, Trewavas recently broke the world record for extreme ironing underwater. Maybe watching the video of her record-setting effort will provide some insight into why anyone would do this. And then again...
• In 2005, Rob Lalumiere led a nine-man technical diver team to set a new deep wreck diving world record of 633 feet. After reaching the deck of the USS Cooper (in 7 minutes), Lalumiere placed a commemorative plaque on the ship, to honor the men who died there in 1944.
• If we're talking "extreme," it doesn't get more extreme than diving with great whites. While cage diving is popular -- especially in South Africa and Mexico -- swimming freely among the world's fiercest fish has gained some visibility lately, thanks to Jacques Cousteau (and *cough* Dave Salmoni).

Of course, these are just some examples of "extreme diving." Have you ever been on a particularly "extreme" dive? Tell us about it!