Carnival Corporation's social-impact brand Fathom announced last month that it is stopping its bi-weekly cruises to the Dominican Republic and Cuba by June 2017.

This is not a huge surprise. It's not that cruise passengers don't care about helping others, but cruising and charity work are strange bedfellows.

Fathom started up last April with a great plan, to bring 704 passengers each week aboard Adonia — formerly of the British P&O Cruises line — from Miami to the north shore of the Dominican Republic. There they would help make improvements in impoverished communities, and get some time in the sun on the way, too.

These vacationers would give up a day at the beach — or at the extravagant pool at Carnival Corporation's Amber Cove port near Puerto Plata — to pour concrete floors, build ceramic water filters, teach English to school kids, and plant trees, activities that were included in the cruise fare.

Within a month of launching, the fledgling line added a second route, cruises to Cuba that took advantage of a loosening of U.S. rules about travel to the island that allows Americans to visit Cuba as long as there are “people-to-people” interactions.

In doing so, Adonia secured a place in history as the first passenger ship in 50 years to sail from the U.S. to Cuba.

The new route was exciting, drumming up a lot of attention, but the line now was selling two completely different products: do-good cruises one week, and cultural exchange cruises the next.

In both cases, Fathom seemed to miss some fundamentals about its audience.

People get on cruise ships to explore, relax, experience a variety of fun activities, eat well, and get good bang for their vacation buck. And while the idea of doing a shore excursion to help out impoverished families has its appeal, spending an entire cruise in the humanitarian realm is a totally different experience.

Also, as ships go, Adonia lacked pizzazz. There was no casino, no stage shows, there wasn't even Caribbean décor.

Another challenge was that target passengers — college students, church groups, corporate team-building groups, the Habitat for Humanity crowd — were mostly travelers who weren’t used to booking cruises. Still, the line’s new mentality succeeded in attracting people in less-likely-to-cruise thirtysomething age range.

And there were quickly signs of trouble. While Fathom's Cuba cruises were commanding $2,000 per person on some one-week sailings, the price of the week-long Dominican Republic cruises plummeted to as low as $199 per person — which was (and is until the line folds) the biggest Caribbean cruise bargain you'll find.

Early passengers on the Dominican Republic cruises talked up their volunteer achievements on land, but complained that there were not enough light-hearted activities on board the ship. So, Fathom added salsa dancing lessons, cocktail-making classes, and wine and paint sessions to a program heavy on life skills workshops and do-gooder cheerleading.

Later, the line added for-a-fee excursions for passengers who didn't want to spend all their time volunteering, so instead they could go zip-lining or snorkeling — a move that somewhat diluted the helping-hand milieu.

When the Cuba cruises started up, passengers quickly opined that they wanted more of a cultural immersion beyond the included people-to-people experiences. For-a-fee shore excursions were added there, too, focusing on topics such as rum and cigars.

For the record, good work was and is being done. By October, Fathom said its passengers had produced and installed some 730 water filters for families in the Dominican Republic, constructed concrete floors in 40 homes, and planted nearly 16,000 seedlings and plants.

Some of that work will continue. Fathom will still operate social impact shore excursions (for a fee) for passengers on Carnival Cruise Line, Holland America Line, Princess Cruises, and other Carnival Corporation brands in the Dominican Republic and in other places around the world. You will be able to book excursions to help out and mingle with local families.

But the line itself is going away. A larger Carnival Corporation ship (which one has not yet been revealed) will be replacing the Fathom ship heading to Cuba beginning in June, pending approval by Cuban authorities. The Adonia will go back to P&O Cruises in the UK.