We stood between a sentinel of Inuit guides armed with rifles on Akpatok Island, an uninhabited outcropping of 700-foot-high cliffs seemingly in the middle of nowhere.

We arrived here at the edge of the Canadian boreal forest a few hundred miles below the North Pole aboard a small vessel operated by Cruise North Expeditions, an Inuit-owned cruise line. The lure: to experience the grandeur of nature in this desolate, frozen land near the top of the world.

On Akpatok, the guides' eyes fixed on the horizon, watching beds of lingering snow for itinerant polar bears. Meanwhile, our eyes peered skyward. Above us, on a sheer cliff as straight as a Marine's back, half a million breeding pairs of thick-billed murres keened in high-pitched voices crackling in the air.

A day later, we approached another outcrop of rocks by Zodiac boat, these stones shaved clean by glaciers 11,000 years ago. We came within 60 feet of a majestic polar bear hunting seal.

This definitely was not your grandmother's cruise.

Most people think the only thing extreme about cruising is the excessive pampering and the volume of food. But you certainly can find voyages that will take you where few dare to tread. A growing cadre of vacationers seeks more extreme opportunities for travel aboard ship, and cruise lines are listening.

If you're looking for unusual cruises, look toward the poles, said Jennifer Gregoire, spokeswoman for Lindblad Expeditions, a renowned name in globe-trotting adventure travel with a roster of voyages to extreme locations. Though Arctic and Antarctic cruises abound, Lindblad and other cruise lines offer adventure vacations in Greenland and Patagonia as well as other parts of the less-tracked world.

You can dive to the bottom of the ocean off the coast of Newfoundland, for instance, to view the remains of the Titanic. The Great Canadian Adventure Co. (www.adventures.ca) hopes to offer these expeditions aboard the Akademik Keldysh, a Russian research vessel, on 11-day excursions next summer. In a submersible capable of descending nearly 2 1/2 miles, the curious and intrepid can reach the resting place of the doomed liner 12,460 feet below the surface. Of course, you'll have to lighten your pockets by about $40,000-plus to do so, said company spokeswoman Vicki Storey.

If you're willing to spend most of your time on land, you could join Wild Lapland Safaris (www.wildlaplandsafaris.fi) for an icebreaker weekend and mini-cruise for about $1,200 (depending on currency rates). You begin your Lapland adventure with a husky dog-sled drive through snowy forests, before departing for Kemi, in southern Finnish Lapland, where you board the Sampo, an icebreaker that operates in the Baltic's northern Gulf of Bothnia.

After four hours aboard the hull-hardened vessel breaking ice at sea, you don special suits to swim in the frigid waters.

Perhaps you want adventure on a small vessel but don't want to forfeit any pampering. Silversea Cruises (www.silversea.com), a mainstay in luxury travel for nearly 14 years, has entered its own uncharted waters with the introduction of the 132-passenger Prince Albert II, Silversea's first foray into expedition cruising.

Among the far-reaching itineraries on the fully renovated vessel: a four-month season of cruises in Antarctica, beginning at $4,256 per person (cruise-only) for an 11-day Chilean fiords voyage departing Ushuaia in November. The fiords cruise plies the waters around the tip of South America only. For sailings along the Antarctic Peninsula, cruise-only fares start at $6,168 per person.

If, however, you want your adventure on a big ship along with a grand casino, gourmet dining, Broadway shows and Vegas revues, as well as penthouse digs to die for, think Crystal Cruises (www.crystalcruises.com) and opt for an extreme excursion instead of an extreme location.

On one Crystal overnight adventure costing about $39,000 per person, for instance, you can don a helmet, signal thumbs up and zoom over Russia's landscape at over twice the speed of sound in a MiG jet fighter.

For more robust sailing adventures, you could join Odysseys Unlimited's 18-day Patagonian Frontiers adventure by land and sea, starting at $5,695. The company (www.odysseys-unlimited.com) offers 12 departures from November through next April. The all-inclusive holiday includes a three-night cruise through the majestic fiords and glaciers of Southern Patagonia aboard the 236-foot-long M/V Via Australis; a three-night stay in Torres del Paine National Park, plus stops in Buenos Aires and Santiago, Chile. By Zodiac, you'll get up close and personal with the Piloto and Nena glaciers and visit Magdalena Island, home to more than 120,000 Magellanic penguins.

The hard-core adventure company Fathom Expeditions (www.fathomexpeditions.com) takes you to both the top and bottom of the world on two unique, customized cruises "in the spirit of the great polar explorers," said Fathom's president, David German.

From July 3 to 13, 2009, Fathom Expeditions sails a 10-night circumnavigation of Svalbard in the high Arctic at 80 degrees north (serious polar bear country). Then, from Oct. 3 to 17, 2009, the company runs a rare 14-night cruise aboard the ice-rated M/V Ushuaia from the Falkland Islands to the jewel of the White Continent, South Georgia Island.

On the high Arctic adventure, passengers will visit the farthest northern island in Europe and get a chance to hike on the oldest rocks in the world, German said. There, they will retrace the routes and landings of North Pole explorers Nansen and Amundsen, he added.

Fares for the 10-night circumnavigation, which departs from Longyearbyen, Spitsbergen, run from $5,500 to $7,500 per person.

On Fathom's 14-night cruise to South Georgia Island (the Galapagos of the South) and the Falkland Islands, German said, passengers will be immersed in a world of Antarctic explorers. "We retrace routes and landings from Shackleton's endurance epic, and we pay a respectful visit to the explorer's grave after hiking Shackleton's route across the island."

In addition, German said, you can count on seeing massive colonies of king, macaroni, rockhopper and gentoo penguins, battling masses of elephant and fur seals, and wandering albatrosses.

Fares for the Antarctica voyage departing Port Stanley run from $6,995 to $9,995 per person, excluding flights.

Lindblad (www.expeditions.com) hosts four cruises to the White Continent as well as to South America and Africa next year aboard two 148-passenger sister ships, National Geographic Endeavour and National Geographic Explorer, with fares starting at $10,250 per person. The schedule: