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.

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.

Gran Cañon is a wall and reef dive located in the Cantabric Sea off San Sebastian. Reaching a maximum depth of 14 metres, this site is suitable for beginner divers looking to gain experience on vertical terrain. Access is by boat, and the site features a mild current. Visibility at Gran Cañon is variable, so it is advisable to check local conditions before planning a dive. Species recorded around this area include wrasses, common octopus, marbled electric ray, scorpionfish, conger eel, and various sea slugs and crustaceans. Divers should confirm appropriate wetsuit thickness with a local centre, as water temperatures fluctuate between 12 and 22 degrees Celsius throughout the year.

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.

Seno Pasajes in San Sebastian offers a combination of natural and artificial reef structures suitable for beginner divers. The site features depths ranging from 15 to 22 metres, with an average depth of 18 metres. Divers can expect mild currents and visibility between 5 and 10 metres. Water temperatures fluctuate between 12C and 21C, necessitating a 4 to 5mm wetsuit outside of the summer months. Access is available via shore or boat, and the site supports night diving. Due to the artificial reef structures, divers should maintain awareness of their surroundings to mitigate entanglement risks. A local dive shop provides equipment hire and site briefings.

Bancha del Este is a shore-entry reef dive located in the Cantabric Sea near San Sebastian. The site features a rocky reef structure reaching depths between 15 and 28 metres. Divers can expect mild currents and visibility ranging from 5 to 10 metres. Due to water temperatures fluctuating between 12 and 19 degrees Celsius, a thick exposure suit is necessary year-round. The site is suitable for beginner divers, though caution regarding boat traffic is required during entry and exit. Species recorded around this area include wrasses, common octopus, conger eels, scorpionfish, and various crustaceans and sea slugs inhabiting the reef crevices.