The best souvenirs from an expedition cruise aren’t T-shirts. They’re experiences that fit a nature lover to a T

We spent the morning hiking the rugged canyons and ridges of Espíritu Santo Island, a protected marine park off the eastern coast of Baja. In the afternoon we snorkeled and kayaked the turquoise waters of its bay. Finally, in the evening, 40 of us, all passengers sailing aboard the National Geographic Sea Bird, sat around a beach campfire roasting marshmallows and listening to gentle waves lap the shore. Millions of stars shone overhead.

Was this a cruise? Or a scout camp?

Sometimes it’s hard to tell the difference when you’re on an expedition ship, which may explore the waters off Latin America or still more remote areas such as the Arctic or Antarctic.

If you dislike the idea of cruising because you fear you’ll be rubbing shoulders with 4,000 people on a passenger ship that’s equipped with giant water slides, climbing walls and ice rinks, maybe you should check out expedition or adventure cruising, which is growing by leaps and bounds.

Expedition cruise lines cater to adventure-seeking travelers who enjoy wildlife viewing in far-flung places, whether Ecuador’s Galápagos Islands or here Espíritu Santo in the Sea of Cortez, also known as the Gulf of California.

“Other ships sail port to port,” said the Sea Bird’s captain, David Kay, explaining the difference. “We don’t. We stop to see wildlife, to take hikes and to have experiences rather than take you to souvenir shops.”

The cruise I took earlier this month, Lindblad Expeditions’ Base Camp Baja, held in alliance with National Geographic Expeditions, was only four days long, a rarity among expedition voyages.

Most are at least a week; some are much longer because they explore far-away destinations. But it gave me a taste of the genre.

I flew from LAX to Cabo San Lucas, Mexico, then hopped on a bus with other passengers for a 2 1/2-hour trip to La Paz, where we set sail.

The Sea Bird has little in common with large cruise ships. The vessel, built in 1982, is elderly compared to many passenger ships — National Geographic calls it “a tried-and-true expedition ship.”

It’s just 164 feet long, carries only 62 passengers and has none of the bells and whistles found on big ships: There’s no casino, no pools and just one restaurant. No cabin is larger than 120 square feet; all are equipped with tiny, awkward-to-use combination toilet-shower stalls.

But most passengers don’t care; they’re not interested in mega-ship trappings.

“The caliber of the staff is high, and the company has a strong environmental ethic. I like that,” said Jennifer Howse, a Brooklyn, N.Y., resident who was on the Sea Bird voyage. This was the third Lindblad/National Geographic trip for Howse, who also has been on expeditions to the Galápagos Islands and Costa Rica. “I like the places these ships go,” she said.

Indeed, many passengers said they choose expedition cruises because of interesting destinations that big ships can’t access. They also like the educational aspects of the cruises, which focus on the history, culture, geology and wildlife of the area. In addition, there are usually staff photographers onboard who offer lots of one-on-one tips.

The uninhabited islands of Isla Espíritu Santo, a protected World Heritage site, are a prime example of a typical expedition cruise destination. Although hundreds of mega-ships call annually at Cabo San Lucas, only small ships like the Sea Bird visit the Sea of Cortez. The islands of this protected marine park feel worlds away from the tourist beaches of Cabo.

“When you go on this kind of trip, you don’t get the amenities you do on a big cruise ship,” said Randy Malcolm of San Diego. “But you get to see places you would never be able to reach. And you don’t have to stand in lines.”

A lack of lines is also important to Anne and Bob Johnson of Long Beach, who have been on multiple expedition cruises, most recently on trips visiting the Antarctic and the Arctic with One Ocean Expeditions, a Canadian company that specializes in polar excursions.

“A key for us,” said Anne Johnson, “is to be able to take advantage of everything that’s offered. We don’t want to get shut out because there are too many people aboard who want to do an activity.”

Expedition cruises also draw praise from passengers because they’re more social. Malcolm likes that aspect too. “No one knows who you are on a big ship; on this kind of trip everyone is friendly, everyone knows your name.”

Because of the growing popularity of expedition trips, more cruise companies are testing the waters, building smaller ships and trying to challenge longtime favorites such as Lindblad, which has a 51-year history of expedition travel.

Fifteen new vessels are being constructed over the next two years, including a mega-yacht from Crystal Cruises, which will launch in 2019 and be equipped with two mini-subs and two helicopters.

Other mainstream cruise companies offering small-ship sailings to places such as the Galápagos Islands are Celebrity Cruises and Seabourn Cruise Line, which will cruise the Arctic Ocean this summer on a 24-night voyage from Reykjavik, Iceland, to Montreal.

Lindblad has geared up too, launching its first new ship, the National Geographic Quest, last July. A sister ship, the National Geographic Venture, will launch later this year. Lindblad’s first new polar vessel will arrive in 2020.

Expedition/adventure cruises usually are pricier than standard big-ship cruises, due in part to the remote destinations. An expedition cruise to Antarctica, for instance, ranges from about $4,000 to $16,000 per person, double occupancy, if you boarded in Argentina or Chile. Add to that the cost of airfare from Los Angeles to South America.

Lindblad’s Baja Base Camp trip was $1,990 per person, double occupancy. When it’s offered again in December and January 2019, it will be four nights instead of three and be on the new ship Venture. Rates will begin at $2,650 per person, double occupancy.

The Sea Bird is currently doing nine-day Baja whale-watching cruises with rates from $6,590 per person, double occupancy.

I’d love to go on one of those trips too, but I enjoyed the Baja Base Camp trip. It varied a bit from most cruises because it had a wellness component, offering yoga and massage from Exhale, a boutique fitness company.

We did yoga on the top deck every morning and yoga on the beach every afternoon. Some people even did yoga on paddleboards floating in the gulf.

I passed on that class and went swimming instead. I figured that was what I’d end up doing, one way or another.

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