Once-in-a-Lifetime Tour Operators

Absolute Adventures (http://www.sharkdiver.com, Tel. + 1 877.820.6589)
Arrange shark diving off the coast of the USA and Mexico.
Mad Dog Expeditions (http://www.maddogexpeditions.com, Tel. + 1 212 744 6763)
Extreme diving operator that do ice diving in the Arctic, heli diving in Papua New Guinea, dive with dolphins in the Amazon and explore countless historic ship wrecks around the world.
Marine Dynamics (http://www.greatwhitesharkcagediving.com, Tel +27 (0) 28 384 1616
Cage diving with sharks off South Africa.
Adrenalin (http://www.adrenalin.com, Tel. 133 791 793)
Air, land, water and motor sport adventures. Based primarily in Australia but also has international destinations.
Explore the Outback (http://www.austcamel.com.au/explore.htm, Tel. + 61 8 8634 7079)
Camel safaris based in the central Australian deserts near William Creek along the Oodnadatta Track.
In The Saddle (http://www.inthesaddle.com, Tel. +44(0) 8700 133 983)
Specialize in horse riding holidays from ranches in the Rocky Mountain states of Montana and Wyoming, to beach and mountain rides in Europe, horseback safaris in Africa and Mongolia.
Arctic Odysseys (http://www.arcticodysseys.com, Tel. + 1 (206) 325-1977)
Pioneers of high arctic travel taking small groups to the North Pole, Arctic Canada, Alaska, Greenland, Iceland, Spitsbergen, Russia and Antarctica. Journeys include dogsledding, icebreakers and journeys to see polar bears, reindeer and penguins.
Tribes travel (http://www.tribes.co.uk, Tel. + 44 01728 685971)
Offering fair trade travel in small groups to Africa, Asia and South America.
Great Southern Railway (http://www.gsr.com.au, Tel. +61 8 8213 4592)
Fabulous train travel options around Australia.
White Wilderness (http://www.whitewilderness.com, Tel. + 1 (800) 701-6238)
Explore trails in the Boundary Waters Wilderness with a dog sled.
Incredible Adventures, Inc (http://www.incredible-adventures.com, Tel. + 1 941 346 2603)
Experience flying in a Russian jet, Zero G flying, sky diving over Everest and a lot of other amazing adventures.
Celestis (http://www.memorialspaceflights.com, Tel. 713-522-7282)
Space flights for memorial occasions.

Do-It-Yourself Options

Unfortunately a lot of these once-in-a-lifetime options are not possible in the do-it-yourself mode unless you own or have access to a MiG, hot air balloon, deep-sea submarine or dog sled. However diving, biking, ice fishing, hunting and many other activities are all possible by yourself.

You should make sure your skills are up to the challenge. For example cave diving has claimed the lives of even the most experienced of divers so think twice before you tackle an underwater labyrinth without the necessary know-how. Even sea kayaking adventures can end in grief for world champion paddlers.

If you’re thinking of going it alone you need to have thought through all the possibilities in regards safety and trip preparation. Make sure someone knows where you are going, and check in with them regularly.

Many operators maybe able to assist you with the gear, maps and equipment needed for solo operations. If you are trying to outfit a car for lengthy trips a lot of websites will outline a preparation schedule and list things to pack.