One of the many great scenes from the film African Queen occurs when Humphrey Bogart and Katherine Hepburn, believing they are doomed, are left prostrate from exhaustion on the deck of the African Queen after trying to navigate the boat through a particularly difficult section of reed-choked river. Only they fail to realize that they are at the end of the impediment, and calmer waters ensue. 
Yep, that's adventure cruising. (And that doesn't even include fleeing, then chasing Nazis.) While today's cruising environment lends itself to relaxation, pampering and gastronomic pleasures, some cruise lines are targeting vacationers who are keen on adventure.
Many of these lines are part of the Niche Cruise Marketing Alliance (NCMA), which is, as the organization's name declares, a group of like-minded cruise lines that cater to a niche market. Cruisers wanting to hike and swim in the Galapagos or brave the ice of Greenland certainly fall within a niche market, as many others would rather sip espresso at a Venice café or lie face down on a pool chair somewhere off the coast of Belize. We're not faulting them—the image of frostbitten toes gives us the willies, too. But, as in any business, if there is a market for it, there's a cruise line happy to cater.
We should get a few things straight right off the bat. If you are looking forward to over-the-top entertainment and shows, anticipate winning millions at the ship's casino or seek a sedentary vacation that keeps you parked on your rear, adventure cruising is definitely not for you.
That's not to say that cruise ships offering more adventure-driven itineraries don't have a slew of nice onboard amenities: Cuisine is often top notch and guest quarters offer most of the same comforts that mainstream cruise lines do. But who wants to sit in their room, anyway? If you're on one of these cruises, it's because you want to get out.
There are certain territories in the world that better lend themselves to adventure cruising. The Bahamas is not one of them; the Arctic and Antarctica are. Don't get the two confused: While you can observe penguins in Antarctica, a polar bear in the Arctic can eat you. 
Great Explorations
One of the leaders navigating the icy straits of the North and South Poles is Lindblad Expeditions, which also offers cruises in the Galapagos, Baja, California, and Alaska. Lindblad's credibility in the expedition cruise market is solidified by its alliance with National Geographic, which was extended in September.
All 12 Lindblad ships now incorporate the National Geographic name (before the announcement, only Lindblad's National Geographic Endeavour carried the distinction). The partnership also combines National Geographic researchers and explorers with Lindblad personnel to offer guests exciting, educational voyages.
Lindblad, however, is only one of a growing number of adventure-centric cruise lines. The steady influx is a testament to the burgeoning popularity in expedition sailing. Though lines such as Hurtigruten, Fred.Olsen Cruise Lines, Galapagos Explorer II, Orion Expedition Cruises and Voyages of Discovery have been standard fare in the adventure cruise market, other lines are making forays into the niche.
Adventure Plus Luxury
Enter Silversea Cruises, which is known more for champagne and caviar than nature treks and dog sledding. The luxury cruise line purchased an expedition ship, World Discoverer, in September, saying it had its eye on the adventure-driven market for some time. Of course, it still is Silversea, so after a multi-million refurbishment, you can expect some of the luxury amenities that the line is known for, such as a specialty restaurant, salon and cigar lounge.
But let's be honest, if you are visiting a vast wonderland like Greenland and long to get your hair done, perhaps adventure cruising is not your cup of tea. If, on the other hand, jumping into a Zodiac and getting your hair a little wet interests you, then adventure cruising may be right—and Hurtigruten, formerly Norwegian Coastal Voyage, may be your go-to line in Greenland, a destination that's attracting global curiosity due to polar-cap melting. Hurtigruten's MS Fram was built specifically for Greenland's environment, which is fraught with splintered sections of ice and larger icebergs.
Though places like Greenland and Antarctica shout adventure, you don't necessarily have to freeze. There are also the Galapagos Islands, which are about 600 miles west of Ecuador and provide opportunity to observe countless endemic species including penguins, nesting marine turtles, sea lions and lava lizards.
The ship Galapagos Explorer II, as the name suggests, is dedicated to sailing in the Galapagos region. The ship offers two shore trips per day, which include walking, hiking, snorkeling, diving and swimming. The Galapagos itinerary is physical, with programs designed to observe the area from different perspectives.
Though no official statistics exist regarding the overall rise in adventure cruising, it is estimated that the market has more than doubled over the last five years and is poised to increase at that same rate over the next five years, according to the NCMA.
The addition of more adventuresome and rigorous shore excursions are a testament to the rising trend. While not occupying the same exposure level as the more mainstream lines and their Car-ibbean and European programs, adventure cruising is gradually gaining steam as a viable alternative.