Last week, Iran assumed the position it had long threatened to take, that of the troll under the bridge determining which ships can pass into and out of the Persian Gulf. Maritime traffic through the Strait of Hormuz was throttled down to almost nothing, and the next phase of the war—predictable to anyone who has thought about what a war with Iran might look like, or who has ever looked at a map—became clear. The United States and its Arab allies will try to keep oil and gas flowing out of the gulf, and food and other goods flowing in. Iran will try to stop them and make life in the desert metropolises of Kuwait, Bahrain, the United Arab Emirates, and Qatar unlivable. With Iran threatening to attack, points of entry to the strait are ready to turn into sprawling maritime parking lots, filled with idle ships waiting for their escorts.When my flight out of Dubai was canceled, I had an idle day of my own. On Thursday, an Iranian drone hit 1,000 yards from my hotel. On Friday, another hit 500 yards away. Just in case the Iranians’ aim was improving by 500 yards every day, I figured Saturday would be a good day for an excursion while I waited for a flight home. That is how I ended up on a snorkeling trip in the Strait of Hormuz.To get to the strait, I drove north from Dubai through several smaller emirates, and watched as the buildings grew shorter and less glassy, until they topped out at one or two stories, and finally gave way to desert. I passed under the quizzical glances of Emirati border guards and endured polite questions from Omani security. No one else was making this journey. After satisfying themselves that I was not intending to engage in amphibious invasion, the Omanis let me in, and I drove onward along an empty coastal highway.The strait is best known for the passage of oil. But its dramatic geography has attracted tourists for years. On the southern side of the strait, a rugged peninsula of limestone cliffs juts up into the gulf toward Iran. The peninsula, called Musandam, is an exclave, a section of Oman cut off from the rest of the country by the United Arab Emirates. And although the strait itself could soon see dramatic naval warfare, the peninsula is quiet because Oman has labored for years to maintain good relations with Iran. In recompense for these efforts, Iran has attacked it only lightly, with drone strikes on the ports of Duqm and Salalah, both hundreds of miles away.The cliffs of Musandam are riven with inlets called khors, often translated as “fjords,” though if you come here pining for Norway you are likely to leave unsatisfied. The cliffs are light reddish and hundreds of yards high—so steep that an intrepid diver could find many points from which to plummet into the water below. They are almost barren, baked into sterility by tandoori levels of heat and harsh sun. The only plants visible from a distance are the thorny local species that tolerate this climate, and survive on a few drops of rain.[Phillips Payson O’Brien: Why Trump didn’t plan for the Strait of Hormuz]On the way into the main city of the peninsula, Khasab, I stopped at a gravel lookout to observe the strait itself. The water was calm and empty, and the nearest Iranian coastline just out of view. Just below, near Khasab, dozens of boats were bobbing, waiting for the signal that they could proceed with their normal activity.An Omani named Mr. Yunus met me there and narrated the scene. He is a seagoing man himself. (And appropriately named: Yunus is the Arabic name of Jonah, the hapless prophet swallowed and then puked out by the whale.) He spoke fondly of Larak, the Iranian island on the other side of the Persian Gulf where he has family. He is Kumzari, a member of the ethnic group native to Musandam, and said that in normal times he could reach Larak by speedboat in an hour and a half. He said the boats below us went back and forth to Iran constantly, in a flow perpendicular to the hydrocarbon transit that the rest of the world has focused on. The war has split the world of these Kumzari mariners in two.For the day at sea, I chartered a dhow: a wooden, square-sterned ship, perhaps 45 feet long and rigged for passengers. The dhow is as distinctively Arabian as the trireme is Greek, or the junk Chinese. In other words, it is perfect for a tourist who wishes to feel like he is partaking in the ancient culture of the western Indian Ocean, even though he has just paid for his journey by Mastercard. The deck was lavishly arrayed with red carpets and cushions. Two Indians were my bored but capable crew.A photograph of Graeme Wood at a marina on the edge of the Strait of Hormuz.We went not even a mile into the strait itself, though we could have gone much farther without any derring-do. We stopped for a wondrous sight: a pod of humpback dolphins, leaping out of the water and playing just off the dhow’s starboard side. For about 20 minutes, they jumped around us, drifted along the bow, and generally acted as our naval escort as we headed toward the khor just east of Khasab. I have seldom seen animals so playful around humans. Perhaps some marine biologist can explain why they would loop around our dhow, and occasionally dive under its hull and pop up on the other side, other than for their amusement or mine.The only sign of human life at sea was the boats we left behind around Khasab. They had been idling—and then, suddenly, I saw a few spring into action. They were not dhows, but smaller, faster boats powered by the engines Mr. Yunus had told me could reach Iranian shores in just over 90 minutes. He had said that in normal times these speedboats departed constantly, but now I could see only the most audacious among their captains heading across the strait to Iran. They were smugglers, he said, and used to living outside the law. Their cargo from the Arabian Peninsula was electronics, and on the return trip, goats. This is how Iranians get their iPhones and how residents of Dubai get their mutton biryani. Uninsured by Lloyd’s of London or anyone else, these men were not about to let a little war get in the way of business.Nor was I going to let it get in the way of my vacation. The dhow’s captain leaned hard into the tiller and steered into the fjord. For the rest of the day, I saw no one other than my dhow-mates. We passed Omani fishing villages, all appearing empty, probably because of the extended snooze people take to pass the hot days of Ramadan. These villages are surrounded by cliffs and unreachable by land. The captain told me the government regularly comes through to replenish freshwater supplies.[Kathy Gilsinan: America’s free-rider problem in the Strait of Hormuz]In quiet parts of the fjord, we stopped to snorkel in the shade of the dhow. The first mate threw chunks of banana into the water, and neon damselfish darted around me to nibble on them. The scene was peaceful and silent, and except for the film of algae that covered me after I splashed about, wholly pleasant and relaxing. The captain, too, seemed content, and at one point donned a mask and snorkel of his own, eased into the water, and speared a five-pound cuttlefish for his supper.For the last excursion of the day, I swam ashore and took a short hike, up 440 steps built into a cliffside. These led to a vista from which one could behold the Persian Gulf on one side and the Gulf of Oman—the entrance to the Indian Ocean—on the other. Goats mocked me as I strained up the final steps and winced at the beginnings of a sunburn on my shoulders. From the top, in each direction, I could see an empty sea, walled by sterile and jagged limestone. I was alone: even the goats preferred lower elevations. In the peaceful shade one could easily forget that World War III might be starting on the other side of the cliffs.