TOURISM IN CUBA is often run by the military. María la Gorda is operated by Gaviota S.A., Cuba's largest tourism company, itself a wholly owned subsidiary of the Revolutionary Armed Forces. The pilot of one sightseeing helicopter told me he'd learned his trade in a Soviet gunship in Afghanistan; my domestic flights were all on Gaviota planes, painted in bright yellows and tropical greens but listed on airport monitors as FAR, Fuerzas Armadas Revolucionarias. Through Gaviota, the military offers fishing expeditions, diving excursions, and trips to thermal baths, and all over Cuba, TransGaviota taxis can whisk you from Gaviota restaurants to Gaviota hotels stocked with Gaviota Hoteles Body Lotion.

At the bar of one such military-tourism complex, the Hotel Nacional, in Havana, I ran into Wayne Smith, a bearded ex-diplomat who was Jimmy Carter's man in Havana, heading the U.S. Interests Section, the closest thing our government has to an embassy here. Wearing a guayabera shirt, he was sitting in a wicker armchair on the back terrace of this stone palace. Musicians strolled past, as in the days when Al Capone, Winston Churchill, and a pile of movie stars slept here.

Smith now directs the Cuba program for the Center for International Policy in Washington, D.C. He'd known Castro for decades, so I asked if El Comandante was really responsible for Cuba's green successes. "Who knows?" he said. "Fidel is a diver. But it is a very mixed record. Cuba has very strong policies in favor of the environment, but on an institutional level, when it is a question of development versus ecology, it slips through the cracks. What's it look like to you?"

The usual, I said: visionary declarations, and then chaos. He grunted. The Cuban environment was just like this hotel: museum more than refuge, protected and neglected, the state skimming off the top and excluding Cubans at the door.

David Guggenheim, an adviser to the Harte Research Institute for Gulf of Mexico Studies, recently told The New York Times that diving in Cuba was "like going back in time fifty years," and I'd assumed as much at María la Gorda. But Smith wasn't having it: In the 1950s, he said, "You never went out without seeing schools of barracuda, sharks, clouds of fish." Now, he said, "most of it's gone. People need the fish, the protein."

That night, I tasted sustainable ocean policy for myself at La Divina Pastora, a restaurant in an old Spanish fortress across the harbor. Cuba uses holistic techniques to breed up a healthy lobster population, with habitat improvements, Fidel's live wells, and catch limits enforced with a ruthlessness that only a dictator could achieve. (The private sale of a lobster is a crime in Cuba; police hunt down black-market lobstermen as if they were crack dealers.) This allows Cuba to export frozen seafood to Europe and Caribbean resorts but also benefits Americans: Since lobster larvae drift up the Gulf Stream, Cuba's management actually helps restore American waters.

The restaurant was run by Gaviota. Dressed in a Hawaiian shirt, the maître d' introduced himself as "Revolutionary Armed Forces Lieutenant Colonel Gerardo Tur." Gaviota, he conceded, had "a close, very direct relationship" with the military. He himself had been seconded to the front lines of the tourism struggle and bragged of having "the best wine list in Cuba." I didn't test him, ordering a daiquiri instead, and then, sitting behind a line of nine iron cannons, ate fresh-picked lobster meat with lime mayonnaise.

Behind me was El Morro, the lighthouse-in-a-castle that is Cuba's most famous landmark. Down the sea wall I could see the U.S. Interests Section, glowing with anti-Castro propaganda and flanked by retaliatory billboards of Uncle Sam having his butt kicked by sexy Cubans.

At 9 P.M., the harbor gun went off, just as it has for centuries. It used to mean the port was closed for the night. These days, it is a starter pistol for the debaucheries to come.