It’s difficult to find a bad bottle of wine in Croatia—afterall, the country has been perfecting its craft for over 2,000 years. Most oenologists (wine specialists) in the region generally stick to the winemaking methods honed across millenia, but one renegade winery is breaking tradition. I traveled across the Atlantic, hopped on a ferry in coastal Ploče, and rumbled down the unfrequented streets of the country’s most famous winemaking region in pursuit of a truly unique inebriant aged in Croatia’s first underwater winery.

Edivo Vina winery is in the town of Drače on a thin strip of land called the Pelješac Peninsula attached to the Dalmatian coast. The mainland is split along the political faultlines of the former Yugoslavia—a five-mile wedge of Bosnia and Herzegovina called Neum slices Croatia into two pieces. When I visited, travelers had to take a ferry to the port in Trpanj or cross the Bosnia and Herzegovina border to get to Drače. Now, a long-anticipated bridge shortens the commute between the island and the mainland. “We’ve been waiting for this bridge for 30 years,” Edivo Vina wine bar manager Nevena Pandža tells me on the morning we arrive. The bridge would open, in a flurry of fireworks, just one month after I landed back in San Francisco.

The relative inaccessibility of the area makes our quest feel more adventurous somehow, like we are hunting for a true sunken treasure. Our prize is Navis Mysterium. Plucked from the sea after spending up to two years at a depth of 65 feet, the wine has been rocked to sensory perfection by the gentle swell of the ocean. The name of the wine literally translates to “the Ship’s Secret” because the bottles are housed inside a Game of Thrones prop ship that the winery sank offshore. Scuba-certified visitors can dive down and see the underwater wine for themselves, led by the three winery owners who are lifelong divers and PADI instructors. “People see the ship and come back happy,” Pandža tells me. “You can see something in photos or videos but when you actually dive down and touch the bottle, that’s really something amazing.”

My buddy Kevin and I are visiting the winery to witness the entire process from sea to glass. We tour the wine cellar first, then head to the dock for our dive. The sun is hot as we transfer our gear onto Edivo Vina’s small skiff and motor up to a floating dock. We giant stride off the dock and descend 10 feet, where a rope attached to the pier is waiting to guide us to the ship. The visibility is worse than in other areas of Croatia, so I am grateful for the line. A hazy dusting of fine particulate hangs in the water column obscuring the size of the ship as we approach. More than 20 crates are stacked on the deck, each one filled with inverted amphorae. Someone has cheekily placed a plastic skeleton holding a sword at the helm of the ship, a treasure chest filled with faux-gold coins at its feet.

Under the waves, this wine enjoys perfect aging conditions: It is insulated from light, kept at a consistent temperature and safe from air—oxygenation is a formidable foe to fermenting grapes, explains Giuseppe Cossu, a Sardinian sommelier. Aging wine underwater is a practice that has been around for millennia, he says, but it hasn’t always followed the same process as Edivo Vina’s. “In Sardinia there is at least one producer who is experimenting with submerging the grapes in cages and keeping them there for a period before crushing and fermenting them. This treatment is more to ‘sanitize’ the grapes with the seawater, and add sapidity to the wine,” Cossu says. But Edivo’s practices have been perfected and honed over the years and through many, many broken and ruined bottles.

“Everything that could have gone wrong, went wrong,” Pandža says. During their first couple of years, the team lost half of the wine they attempted to sink, mostly due to saltwater intrusion. But now the process is as well-oiled as an Italian olive. The bottles are placed in locally-made clay amphorae, which are then filled with insulating foam. The bottles are sealed, with wax and then cement, to keep seawater out and wine in. Edivo Vina also ages some “naked” bottles without the clay amphorae. These are attached to ropes and hang in the water, an aging process that requires fewer variables and is less challenging.

After two years, the bottles are removed, cleaned and soaked in fresh water for one month and then dried in the cellar before they are sold as wine with “a little bit of sea in it,” Pandža says. The finished bottles are encrusted with marine traces, like oyster shells and invertebrate casings, and perched on handmade iron stands. They look more like art than wine.

Unboxing the final product is Pandža’s favorite part of the job: “I like seeing people’s faces the moment I open the box, and they go: ‘Wow!’” she says. That reaction explains why visitors are willing to shell out the 2875 kuna (about $370) for each completely one-of-a-kind bottle.

While Navis Mysterium’s process is unique, it’s anchored in a deep culture. “In every house in Croatia, wine is always included in life,” Pandža says, “I first tried wine when I was three or four years old. My grandparents would take a finger of wine and fill the rest of the cup with water and that was juice for us.”

Back at the tasting room after our dive, we try a side-by-side comparison. To my surprise, the wine that had spent two years underwater was noticeably different from the cellar-aged wine, even to my novice taste buds. The pressure has deepened the flavors, bringing out a richness that sends a jolt of warmth through my nitrogen-laden body as I sink into the indulgence of the moment. It lingers on the back of the palate far longer than I can hold it between my teeth. The salt on my upper lip mingles with the flavors dancing across my tongue—a bit of sea in every sip.

Need to Know

Cost: Edivo Vina dives include a ship tour, a full-flight tasting of their underwater wines (which is accompanied by a local snack platter of fish, cheese, homemade gluten-free bread, and smoked meats), and a bottle of undersea wine to take home. The cost of the tour and tasting is €200 or €240 based on the inclusions. Tours can be booked at edivovina.hr.

Equipment: The winery provides all gear, weights and tanks for the dive, as well as transportation from the wine bar to the dive site and back.

Topside Tip: Head into Trstenik, a short drive from the winery on some very windy narrow roads, to enjoy a scenic Mediterranean meal and local oysters at D’ORO Bar & Grill. If you’re lucky, you might even get to try some homemade liqueur while you dine on the spacious waterfront terrace.