Ondartxo is a diverse marine site located in the Cantabric Sea off San Sebastian, Spain. The topography features a combination of reef, wall, and cave formations that descend from 14 to 32 metres, with an average depth of 18 metres. Access is exclusively by boat. Divers should be prepared for variable visibility and currents, requiring solid buoyancy control and navigation skills. Water temperatures range from 12C to 19C, necessitating appropriate thermal protection such as a drysuit or thick wetsuit. Due to the depth and potential for shifting conditions, this site is best suited for intermediate divers who can manage variable currents and monitor their depth profile carefully.

Bajo de las Gorgonias is a reef site located in San Sebastian, Spain, accessible only by boat. The reef structure extends from the surface to a maximum depth of 26 metres. Divers should be aware that visibility is variable and requires local verification before planning a trip. The site experiences mild currents, making it suitable for intermediate divers. Water temperatures fluctuate between 12C and 20C throughout the year, necessitating appropriate thermal protection. Species recorded around this area include wrasses, common octopus, conger eels, scorpionfish, slipper lobsters, and various nudibranchs. Due to the depth, divers must monitor their gauges closely to maintain a safe profile.

Astillero is a pinnacle located 500 metres offshore in the Cantabric Sea. The structure rises from a maximum depth of 27 metres to a shallow point of 5 metres. Divers and snorkellers can expect mild currents and visibility ranging from 10 to 20 metres. Due to the sharp drop-offs and significant depth, buoyancy control is essential. The site is accessible by boat and is suitable for beginners, with typical dives lasting around 40 minutes. Night diving is permitted at this location. Shore facilities available for visitors include parking, toilets, showers, changing rooms, a rinse station, air fills, equipment rental, and boat charter services.

La Redonda in San Sebastian offers a diverse underwater landscape combining reef, wreck, and cave diving. Located 200 metres from shore, this site is accessible by boat and suitable for beginners. Divers can explore depths ranging from 10 to 21 metres, with an average depth of 17 metres. Visibility reaches up to 20 metres, though conditions vary. The site features mild currents and water temperatures between 12 and 21 degrees Celsius. Divers should maintain good buoyancy control to avoid entanglement hazards within the wreck and cave structures. Night diving is permitted, providing opportunities to observe nocturnal activity. Local facilities include equipment rental, air fills, and boat charters.

Cala Illurgieta is a reef dive located in the Cantabric Sea near San Sebastian. The site features a reef structure that descends from 8 metres to a maximum depth of 24 metres. Navigation is manageable for beginners due to the mild currents present. Divers should note that visibility can vary between visits. Access to this site is by boat only, and guided tours are available to assist in locating smaller marine life on the reef surface. Given the water temperatures, which range from 12C to 20C throughout the year, a drysuit or a 7mm wetsuit is recommended for comfort.

Cañonero el Tajo is a wreck and wall site located in the Cantabric Sea near San Sebastian. The site features a sunken vessel resting against a wall, with depths reaching 25 metres. It is accessible by boat and suitable for beginners due to the mild currents. Divers should maintain awareness of their depth and exercise caution when navigating the wreck structure to avoid sharp elements or entrapment. Visibility is variable, so conditions can change between dives. Water temperatures range from 12 to 20 degrees Celsius, requiring at least a 5mm wetsuit for thermal protection throughout the year.

El Seno in San Sebastian offers a varied underwater environment combining reef, wreck, and drift diving. Located in the Cantabric Sea, the site reaches depths between 10 and 21 metres. Divers should expect visibility around 5 metres, making this an intimate, close-up experience. The current is generally mild, though divers must remain vigilant regarding active boat traffic on the surface and potential entanglement risks when navigating the wreck sections. Water temperatures fluctuate between 12 and 21 degrees Celsius throughout the year. The site is suitable for intermediate divers and supports night diving, which provides opportunities to observe the local marine life in the open.

El Colector is an artificial reef located in the Cantabric Sea near San Sebastian. The site features a man-made framework that reaches depths of up to 25 metres. Accessible only by boat due to significant surf and shore break along the coastline, the site is suitable for beginners, though variable currents require careful monitoring. Divers should remain aware of changing conditions, as currents can strengthen unexpectedly. The structures provide habitat for a variety of marine life, including spider crabs, lobster, octopus, cuttlefish, scorpionfish, and bream. Sea fans, anemones, and nudibranchs are also found on the reef framework. Water temperatures range from 12C to 20C throughout the year.