Winemakers pioneer underwater fermentation in Saint-Jean de Luz bay

In the bay of Saint-Jean de Luz, just a few meters from the Artha breakwater and the popular beaches, an unusual winemaking experiment is taking place beneath the surface. The Socoa diving center, in partnership with Egiategia, offers divers a unique experience: exploring the underwater world above submerged wine tanks at a depth of 15 meters. This is not simply about aging bottled wine underwater, as some Champagne houses do far from their vineyards. Instead, Egiategia uses grapes harvested within a 150-kilometer radius and immerses them for a second fermentation in specially designed tanks on the ocean floor.

Emmanuel Poirmeur, an agronomist and oenologist with experience at renowned estates, leads this project. He patented his method of underwater winemaking and aging in 2007. The idea came to him while working for Chandon in Argentina, where he realized that the physical conditions needed for secondary fermentation in sparkling wines—pressure, temperature stability, and constant movement—are naturally present in the marine environment.

Poirmeur explains that understanding this process requires letting go of traditional winemaking assumptions. Underwater, winemakers can attempt things that are impossible on land. The wine is placed in bulk into tanks anchored at 15 meters deep. Three main factors define this second fermentation: pressure and its fluctuations, gradual temperature changes without thermal shock (ranging from 6 to 23 degrees Celsius), and constant agitation from tides that keeps the lees suspended.

Each batch of Egiategia wine emerges from the water with unique characteristics. Only blending allows for consistency in certain cuvées. The underwater autolysis and suspension of lees give some wines a richness reminiscent of Burgundian wines aged with bâtonnage. However, there is no single “underwater” flavor profile. Poirmeur notes that even when 60 identical tanks of white wine undergo secondary fermentation together under identical conditions, each one develops differently. This variability is part of what makes Egiategia’s approach distinctive.

Egiategia’s philosophy stands apart from standardization. The process embraces unpredictability and celebrates individuality—a reflection of Basque identity and freedom. Locals fluent in Euskara often ask for a glass of “Egia,” meaning “truth” in Basque, rather than Egiategia.

For those who have not yet tasted these unique wines, there will be an opportunity soon during the Fêtes de Bayonne. Egiategia’s cuvées will be featured at Vignobles et Découvertes inside the bustling Halles market, offering festival-goers a chance to discover wines shaped by both tradition and innovation—and by the ocean itself.