Simon and Carla Fowler are anchored in their catamaran about 650 feet off a deserted beach in the Bahamas, and they have a message for anyone locked down on land who wishes that they too could be self-isolating on the water.

“Being out here in a pandemic is actually a lot harder and more stressful than you might think,” said Mr. Fowler, a 60-year-old British events organizer who has spent the last two years living at sea with his Portuguese-born wife on their 40-foot catamaran.

“It is the most depressing time we have had in two years,” he said. “It has been quite nasty.”

Locals fearing infection have become less welcoming to cruisers like the Fowlers over the last six weeks. Ports and borders have begun closing, supplies have become harder to find, and the couple have to abide by the same social distancing restrictions in place on land, meaning they can no longer socialize with other sailors.

The seas may be the ultimate escape and self-isolating destination, but people aboard everything from solo craft to superyachts say the tranquillity of the waves has come with logistical hurdles and ethical dilemmas. And then there is the bullhorn of social media: the blaring comments and tweets calling them entitled, clueless about the serious struggles of the day.