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.

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.

Pain de Sucre is a compact site located off the Île de Riou, featuring a diverse topography of reef, wall, drop-off, and pinnacle. Divers can expect depths between 20 and 26 metres. The site is defined by strong, shifting currents that require careful planning and energy management during the ascent. Visibility is variable, ranging from 10 to 30 metres depending on conditions. Water temperatures fluctuate between 14 and 19 degrees Celsius throughout the year, necessitating appropriate thermal protection. Access to this site is by boat only, and it is recommended for intermediate divers comfortable with moving water.

Calanque des Contrebandiers is a sheltered reef site located at Île de Riou in the Riou Archipelago. Accessible by boat, the site features a shallow reef environment characterised by mild currents. Visibility at this location typically ranges between 10 and 30 metres. Water temperatures fluctuate throughout the year, reaching a maximum of 24 degrees Celsius in August and dropping to 14 degrees Celsius in the winter months. Divers should plan their thermal protection according to the season. As conditions are generally calm, the site is suitable for those looking for a relaxed diving experience in the French Riviera and Provence region.

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.

Grotte du Corail is a cave and reef site located off the Île de Riou. This site offers a combination of open-water reef diving and an overhead cave environment, with depths ranging from 15 to 30 metres. Divers encounter Mediterranean moray, scorpionfish, wrasses, and various nudibranchs including Cratena slug and tricolor doris. Visibility typically spans 10 to 25 metres. Due to the overhead environment and sharp rock surfaces, solid buoyancy control is essential. The site is accessible only by boat and is suitable for intermediate divers. Water temperatures fluctuate between 14 and 20 degrees Celsius throughout the year, and night diving is permitted.

Tombant de David is a shore-entry wall and drop-off site located at Île de Riou. The topography descends from 10 to 40 metres, with an average depth of 20 metres. Divers encounter moderate currents along the vertical seascape, making this site suitable for intermediate divers. Water temperatures range from 14 to 17 degrees Celsius, necessitating at least a five-millimetre wetsuit. Visibility can be variable, requiring careful orientation in deeper sections. Marine life recorded here includes Mediterranean moray, great barracuda, wrasses, scorpionfish, and various nudibranchs such as the Cratena slug, Mediterranean violet aeolid, and Felimare orsinii. Other inhabitants include cow snails, flatworms, gorgon's head, Turkish wrasse, tricolor doris, flamingo tongue, and squat lobster.