The Etang de Thau (Thau lagoon) is to snorkelers a hidden gem of southern France. Separated from the sea by sand dunes, this salty water lagoon shelters incredible and atypical underwater life. Ponton de la Bordelaise (the Bordelaise pontoon) is a perfect place to discover Thau lagoon. If you plan your visit ahead, you will maximize your chances to spot seahorses (the true stars of this spot), but also pipefish, nudibranch, noble pen shells and several rock fish species.
The Ponton de la Bordelaise spot is located at Thau lagoon’s eastern extremity, between Sète and Balaruc, a ten-minute drive from each of these cities. From Sète, take road D2 towards Balaruc. Leave it right after crossing the bridge over the Canal du Rhône à Sète. Turn right after the first stop sign and look for the unpaved road following the channel, about a hundred meters further on. Follow this road for about 150m until you reach a parking lot. If you’re arriving from somewhere else, use a GPS to get here (coordinates are here). Once your car is parked, walk along the water channel for about 500m until you reach a small red and white lighthouse built at the end of the dyke. The pontoon you’re looking for is visible on your right.
There is one important thing you need to know before going for it: the lagoon is a relatively closed environment in which water temperature variations greatly influence underwater visibility. Consequently, to maximize your chances of spotting species, we advise to plan your visit during spring (April to May), when water is still cool enough to ensure decent visibility. From late May – early June, seaweed pervade the lagoon and visibility lowers down to 6-12ft/2-4m. During summer, visibility can be so bad that entering the water will be of no use, and you might have to turn back home. At some times of the year, it is also possible to find many jellyfish in the area, especially in summer, when the water of the lagoon is warmer.
Enter the water at the foot of the lighthouse, facing the pontoon. Concrete steps will help you sit and put your gear on before gradually entering the water. Be aware of the fact that the spot is located in an industrial area. As a consequence, water is not always clean and waste sometimes pile up on the shore.
The exploration area extends between the channel dyke (from where you will enter the water) and the pontoon. About 100 meters separate them. Water is quite shallow along the dyke and the shore (↕2-6ft/0,5-2m) but it lowers down to 10-12ft/3-4m under the pontoon and at the center of the area. We advise to swim along the dyke all the way to the pontoon so as to remain in shallow areas more suitable for snorkeling.
The seabed is mainly rocky. It is sometimes covered with seaweed, brushwood and shipwreck remains. Numerous sea urchins, anemones, Sabella and a few noble pen shells are set there.
Seahorse spotting is the reason why most people come here. Seahorses live all over the exploration area, so they can theoretically be spotted everywhere. Even if their number vary annually, you will most likely find them if you take a close look around you. Indeed, the main difficulty is to distinguish them from seaweed, branches and rocks to which they cling using their prehensile tails, and to which they are very similar. Even if seahorses prefer mid-depth areas (water depth 1-3 meters), they can also be found in shallow areas. For instance, they have been spotted a few times on the rocks located at the very foot of the lighthouse (↕2-3ft/0.5-1m). The most represented species in Thau lagoon is the long-snouted seahorse (4 to 6 inches/10 to 15cm long). Short-snouted seahorses can also be spotted, though slightly more rarely.
If you have come all the way to spot seahorses, you will love Thau lagoon’s other wonders. It is for a start a perfect place to spot several pipefish species. Those slim fish with bony silhouettes are cousins to seahorses. The greater pipefish is often seen crawling over the bedrock, when the black-striped pipefish swims in open water, sometimes just underneath the water surface. Several nudibranch species also dwell in the lagoon, like the colorful but tiny pilgrim hervia (only 1 to 2 inches/3 to 5 centimeters large). It can generally be seen from late spring on rocks covered with small algae. Aplysia are much larger, they can be observed during summer. The peacock blenny will probably be the first fish you will spot, as it is very present in this area. Males are easy to recognize with the distinctive hump on their head. Several other blenny species and large gobies are also commonplace over the rocks. Once underwater, take a close look on the pontoon’s pillars: some of them are covered with sabella, those marine worms living inside tubes. When they need to feed, they protrude as feathery plumes.
Mind the boats sometimes circulating in the area: do not go further from the pontoon’s end, and make sure you are visible from the water surface. This is a famous diving spot and aqualung divers are numerous here. Be especially careful when visibility is poor.
This spot is located next to an industry and wasteland area deprived of any restaurants or accommodation options. Sète and the nearby villages set along Thau lagoon offer all amenities if you want to buy food for the day or stay in the area.
These spots are accessible to anyone with basic snorkeling skills, and feeling comfortable in the water and with his snorkeling gear. You will enter the water from the shore (beach, pontoon, ladder, rocks) or from a boat. The water height in the sea entrance area is reasonable, but you will not necessarily be within your depth. Moderate currents can occur in the area, even when the sea conditions are good. The distance to swim to reach the most interesting snorkeling areas of the spot does not exceed 200 meters.
This level only apply when the spot experiences optimal sea and/or weather conditions. It is not applicable if the sea and/or weather conditions deteriorate, in particular in the presence of rough sea, rain, strong wind, unusual current, large tides, waves and/or swell. You can find more details about the definition of our snorkeling levels on our snorkeling safety page.
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Snorkeling spots are part of a wild environment and their aspect can be significantly altered by weather, seasons, sea conditions, human impact and climate events (storms, hurricanes, seawater-warming episodes…). The consequences can be an alteration of the seabed (coral bleaching, coral destruction, and invasive seagrass), a poor underwater visibility, or a decrease of the sea life present in the area. Snorkeling Report makes every effort to ensure that all the information displayed on this website is accurate and up-to-date, but no guarantee is given that the underwater visibility and seabed aspect will be exactly as described on this page the day you will snorkel the spot. If you recently snorkeled this area and noticed some changes compared to the information contained on this page, please contact us.
The data contained in this website is for general information purposes only, and is not legal advice. It is intended to provide snorkelers with the information that will enable them to engage in safe and enjoyable snorkeling, and it is not meant as a substitute for swim level, physical condition, experience, or local knowledge. Remember that all marine activities, including snorkeling, are potentially dangerous, and that you enter the water at your own risk. You must take an individual weather, sea conditions and hazards assessment before entering the water. If snorkeling conditions are degraded, postpone your snorkeling or select an alternate site. Know and obey local laws and regulations, including regulated areas, protected species, wildlife interaction and dive flag laws.