If oceanliners are the buses of water travel, river cruises are like limousines — a little more intimate and relaxing.

And river cruises are popping up on all seven continents, a testament to their growing popularity, especially among the over-40 set.

“You’re not doing a lot of moving around; you’re not lugging suitcases,” says Alice Klingerman Stickney, owner of Klingerman Travel in New London. “You walk aboard, unpack and you’re done.”

On river cruises, say travel experts, magnificent vistas roll by every day and new locations offer a cornucopia of cultural, architectural and gastronomical experiences. River cruises can be found virtually anywhere — China, Russia, Vietnam, Australia, the Caribbean and the Mississippi, for instance — but some of the most popular continue to be in Europe.

While river cruises can run from $1,000 to $25,000 depending on the location, the passenger line and the number of days of travel, discounted weeklong European trips generally run between $2,000 and $7,000 a person. Among the most popular trips are along the Danube and Rhine rivers.

And with passengers limited to between 120 and 290 depending on the size of the ship, there’s a little more leeway — than on oceanliners with 5,000 aboard — to suggest sightseeing excursions that may not be on the regular itinerary.

“You can’t do that on the megaliners,” says Inger King, owner of King Travel in Norwich.

Stickney says river cruises allow passengers to be adventurous one day and lazy the next, because there is never any pressure to go on the daily trips. Similarly, people traveling with loved ones who have trouble walking can enjoy the sights, knowing that their companion will be well taken care of on the boat in their absence.

“You do as much or as little as you want,” Stickney says.

And while visiting exotic locations is exciting, eating the local cuisine may be another story for visitors. That’s where being able to return to the riverboat pays real dividends, because the ships can offer passengers more conventional — and perhaps for Western tastes palatable — fare, not to mention accommodating those on special diets.

People with special medical conditions can be accommodated as well, including those on oxygen or requiring dialysis. A doctor can be found aboard all the ships, but insurance is recommended for those over 65 because Medicare does not cover health emergencies overseas.

King says that the Viking line offers at least one shore excursion every day, and the cruises are pretty close to all inclusive. Prior to the excursions, passengers are invited to attend a lecture to learn a bit about the culture and history of the lands they are visiting.

“The rooms are very spacious,” she says. “They’re more spacious than an ocean liner.”

Guests can eat in the dining room or al fresco on a terrace. Some of the cruises offer entertainment at night.

But one of the most delightful aspects of a river cruise, says King, is the chance to get to know other travelers from all over the world. It’s not unusual, she says, for people who were complete strangers a week earlier to book trips together the next time around.

“That’s part of what makes it so special,” she says.

Another part is the changing tableau of scenery as villages, hamlets, cities, fields, castles and gardens pass by passengers’ windows as they travel. And each cabin features water views.

“There’s something special about being on the water,” King says. “It’s a more relaxing way to go.”