L'écueil du milieu is a reef located off the Île de Riou, France, offering a dive experience at depths between 20 and 25 metres. This boat-accessed site features moderate currents that can strengthen, requiring intermediate skill levels to manage positioning and air consumption. Visibility ranges from 10 to 30 metres. Divers may encounter wrasses, scorpionfish, and various nudibranchs such as the tricolor doris and cratena slug. Less frequently, great barracuda, Mediterranean moray, conger eel, and common octopus are recorded. The site is best suited for experienced divers comfortable with depth and current management. Local facilities include air fills, equipment rental, and guided tours.

Calanque de Monasterio is a remote reef site located on the uninhabited Île de Riou. Accessible only by boat, this location features white sandy bottoms and is situated within the National Park. The site is suitable for intermediate snorkellers, offering a 5/5 rating for the activity. Water temperatures fluctuate throughout the year, ranging from 14C in the winter months to 24C in August. Due to its distance from the shore, approximately 14 kilometres, visitors should be prepared for moderate currents. The site provides a quiet environment for observing the underwater topography of the Riou Archipelago.

La Donatello D is a reef and wall site located off the Île de Riou, offering a shallow profile between 9 and 12 metres. This site is well-suited for beginner divers due to the manageable depths and generally calm conditions. Visibility typically ranges from 10 to 30 metres, providing clear sight lines along the reef structure. Access to the site is exclusively by boat, and divers must remain vigilant regarding boat traffic when surfacing. A surface marker buoy is recommended for all ascents. Water temperatures fluctuate between 14 and 23 degrees Celsius throughout the year, necessitating appropriate thermal protection during cooler months.

Les Pierres Tombées, located off the Île de Riou, features a combination of reef and drop-off topography. The site ranges from 15 to 29 metres in depth, with an average of 20 metres. Divers can explore shallower reef sections before reaching the deeper edge. Visibility typically spans 10 to 30 metres. The site is suitable for beginners, though a moderate current requires careful buoyancy management. Marine life includes common scorpionfish and various wrasses, alongside less frequent sightings of Mediterranean moray, great barracuda, common octopus, and several species of nudibranchs and flatworms. Boat access is required, and a 5 mm wetsuit is recommended due to water temperatures between 14 and 18 degrees Celsius.

Grotte de Boulegeade at Île de Riou offers a diverse underwater experience combining a cave system, reef, wall, and drift diving. Depths range from 7 to 45 metres, with an average of 28 metres. Divers encounter moderate currents, particularly near the cave entrance. Visibility typically spans 15 to 25 metres. Marine life includes wrasses, scorpionfish, common octopus, Mediterranean moray, and various nudibranchs such as the tricolor doris and cratena slug. Due to the overhead environment and depth, this site is suited for intermediate divers with appropriate training. Access is by boat only, and a torch is recommended for navigating the cave interior where natural light diminishes rapidly.

Les Moyades, located at Île de Riou, offers a diverse underwater topography consisting of reefs, walls, and caves. Divers can explore depths ranging from 3 to 35 metres, with an average depth of 20 metres. The site requires boat access and is suitable for intermediate divers. Visibility typically spans 10 to 30 metres. Marine life includes common sightings of wrasses and scorpionfish, while uncommon species such as common octopus, great barracuda, Mediterranean moray, and various nudibranchs are also recorded. Hazards include sea urchins, sharp rocks, and overhead environments in cave sections. Water temperatures range from 14 to 18C, necessitating appropriate thermal protection. Night diving is available at this location.

Le Couloir aux gorgones is a boat-access reef located off the Île de Riou near Marseille. The site features depths ranging from 25 to 36 metres, requiring appropriate depth certification and buoyancy control. Divers typically encounter moderate currents, making it necessary to plan dive profiles carefully and utilise the reef for shelter. Visibility at the site varies between 10 and 30 metres depending on local conditions. Water temperatures fluctuate between 13 and 19 degrees Celsius throughout the year, necessitating a thick wetsuit or drysuit for thermal protection. Given the depth and current, this site is best suited for experienced divers.

Les Moyadons is a wall and reef site located off the Île de Riou. The topography features a wall dropping to a maximum depth of 37 metres, with shallower reef sections starting above 10 metres. Divers can expect visibility ranging from 10 to 30 metres. This site requires boat access and is suited for intermediate divers due to moderate currents that can strengthen without warning. Water temperatures fluctuate between 14C and 19C throughout the year. Divers should exercise caution to avoid contact with sharp coral and rock edges along the wall. Planning dives to work against the current during the initial phase is recommended.