The coral wall rose from the depths of the Red Sea, a vast and multicolor canvas brimming with sea life. I swam alongside it for 200 feet, past tangled branches, swaying ferns and brain-like spheres, and then dove toward the ocean floor. A school of black-and-yellow-stripe angelfish darted around me, while a grouper the size of a Smart car lumbered past. Rising toward the surface, I spotted a silver barracuda hovering just below the water line. Abruptly the wall ended, and I rounded the corner to confront a netherworld of rusting cables, ropes, labyrinthine corridors and cabins, and a barnacle-covered anchor.

The dive site I had been exploring for an hour was no natural formation, but the side of an Ethiopian battleship. For the past quarter-century, this corroding wreck has lain on the bottom of the harbor of Massawa, Eritrea’s main port city, slowly colonized by marine life. (The barracuda, my boat captain told me, was one of seven that frequent the sunken ship.) Rebels of the Eritrean People’s Liberation Front bombarded and sank the vessel in 1990, during the last bloody months of Eritrea’s three-decade-long independence war against Ethiopia. The rusting bow and the remnants of its gunwales protrude above the surface, forming a beacon for divers and snorkelers.

Diving holidays are perhaps not the first thing that comes to mind when the subject of Eritrea arises. This impoverished nation in the Horn of Africa — bordered by Ethiopia, Djibouti, Sudan and the Red Sea — was once considered among the continent’s brightest hopes. But after two decades of repression, international isolation and a forced military conscription program that has driven hundreds of thousands of young people out of the country, it has earned a reputation as the “North Korea of Africa.” In 2016, a United Nations report accused Eritrea of “crimes against humanity,” citing the imprisonment and torture of dissidents. Its leaders have been sanctioned by the United Nations for providing aid to Al Shabaab, the Islamic terrorist group in Somalia. (The United Nations Monitoring Group on Somalia and Eritrea reported in 2012 that the government, under international pressure, had ended its direct support of the group.) Visitors have been few and far between. According to the government guides I spoke to, the country received fewer than 1,000 tourists in 2015.

Yet despite its myriad problems, Eritrea is generally safe, though it’s best to check the State Department’s travel website for updated information on travel and security (see below). Its Red Sea coast offers some of the finest snorkeling and scuba diving in the world. The warm waters of the Dahlak Archipelago — a scattering of more than 120 islands, only four of them inhabited, lying just north of Massawa — abound with jellyfish, barracuda, manta rays, parrotfish, red snappers, coral fish, puffer fish, clown fish and more than 200 types of corals. Moreover, unlike the deeper, cooler waters elsewhere in the Red Sea, Eritrea’s shallow, and therefore hotter, waters have created corals capable of adapting to temperature extremes. This unique environment, marine biologists believe, could provide a living laboratory to help endangered coral reefs around the world survive in the face of global warming.