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.

I first visited Massawa in 1993, just after Eritrea formally declared its independence, as Africa bureau chief for Newsweek, then returned three years later, when the media and Western donors were still touting the country as a success story. I hired a dive boat and a guide and for two days explored the pristine reefs of the Dahlak Archipelago, then just beginning to attract tourists.

Two decades later, on a return visit last July, I again ventured to the coast, curious to see how Massawa had fared under Eritrea’s harsh dictatorship, and what was left of the diving industry that, in the 1990s, had seemed poised to grow.

I started my journey in Asmara, the 7,628-foot-high capital, a charming, faded city filled with crumbling Art Deco movie theaters and cappuccino bars that date to Italy’s 50-year colonization of Eritrea. (The British threw out the Italians in 1941.) A permit is needed to visit Massawa, obtainable at a hole-in-the-wall office on Harnet Avenue, Asmara’s main drag. There, I met a guide named Thomas, who was trying to secure permission for a dozen Chinese road engineers.

As we waited for the office to open, he lamented Eritrea’s ravaged economy and the open-ended conscription program. “The prime years of people’s lives are being lost,” he told me. He had used his connections to secure a dead-end posting in a ministry instead of army service, but still dreamed of fleeing. “I think about escaping, every day, but now I realize I missed my chance,” he said, as an official showed up on his moped two hours late and unlocked the door. “It’s too late. The walls have gone up.”

I hired a taxi at a downtown stand, and at 8:30 the next morning, the driver, Zaki, picked me up at my hotel. It was Eid al-Fitr, marking the end of Ramadan, and the streets of this small city were deserted. We drove past the Ethiopian war cemetery, fields of cactus and a herd of camels, and then the Asmara escarpment came into view: a barrier of acacia-speckled mountains that extends almost to the Red Sea. Cyclists clad in red-and-white Lycra worked their way around the hairpin turns; the pop music of Mahmoud Ahmed, an Amharic singer from Ethiopia, blared from Zaki’s CD player. After two hours — and a drop of nearly 8,000 feet — we reached the sandy coastal plain. A quintet of captured Ethiopian tanks marked the entrance to Massawa.

We crossed a causeway and arrived at the Dahlak Hotel, an Italian-owned colossus that decades ago was considered Massawa’s finest. Now it was deserted. The marble-tile staircases, Ottoman-style doorways and palatial salons hinted at the hotel’s 1970s-era grandeur. But my $88-a-night second-floor room — overlooking the bombed-out seaside palace of the Ethiopian Emperor Haile Selassie — had corroding fixtures, a sagging mattress and a broken toilet seat. Entering the saltwater pool, I slipped on the thick layers of algae that covered the steps and nearly lacerated my feet kicking off the barnacle-encrusted wall. The pool floor was a moonscape of ripped up tiles and exposed mud underneath.

Late that afternoon the hotel clerk put me in touch with Abdullah, a grizzled boat captain who spoke some Italian but no English. A friendly English-speaking Eritrean from Asmara who was sitting at the outdoor cafe offered to help me make the deal. The logistics, I quickly learned, had grown complicated. Dahlak Kebir Island, the archipelago’s main attraction, was now off limits to tourists, Abdullah said. Instead he proposed a daylong scuba-diving trip to Dessie Island, not far from Dahlak, for 16,000 nakfas, or $1,020, about five times what I had paid two decades earlier.

“I have no business,” Abdullah explained, pointing to five scuttled dive boats moored across Massawa harbor that had constituted his fleet during better times. “Everything is gone.” Abdullah was open to negotiation, but instead I opted for a half-day snorkeling and beach trip around Green Island, just beyond the harbor. The cost was a far more reasonable $200.