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Provence

Grotte à corail de Riou (Impériaux)

  • Max depth45 m
  • CertificationCavern
  • Water temperature≈ 14–24 °C, varies with the seasonestimated, no reports yet
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Diving and fills

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Fills nearby

  • Fill stationCassis Calanques Plongée~6 min drive (estimate)Nitrox and trimix (tech and CCR courses); which gases visitors can have filled, and to what pressure: askRoute ↗
  • Fill stationKraken Plongée (La Ciotat)~16 min drive (estimate)Air, nitrox, oxygen and helium; fills at 230 and 300 barRoute ↗
  • Fill stationPlongée Tek Marseille~29 min drive (estimate)Fills diluent (air, trimix) and O₂ for its own CCR and trimix students; fills for visitors: askRoute ↗
All fill stations and places to stay ↓

The dive

A deep cave with coral at the Impériaux, three rocks off the south-east tip of Riou. According to one database it is a fine cave with a wall full of gorgonians, visibility 10–30 m and weak current (<1 knot).

Entrance at -35 m: depth and decompression are the main risks here.
Source: Wannadive – La grotte à corail de Riou ↗
Profile and sections

A deep cave with coral at the Impériaux, three rocks off the south-east tip of Riou. According to one database it is a fine cave with a wall full of gorgonians, visibility 10–30 m and weak current (<1 knot). It can be combined with the lit passages of the Impérial de Terre (-15 to -25 m, a rock 'like Swiss cheese', from level 1 with PE40).

Depth and profile
Entrance at -35 m · wall to -45 m
Configuration
Cave dimensions not published — ask a dive centre.
DPV: Not DPV-suitable (estimate)
Deep boat and wall dive; a scooter gains little in the cave.
Who can dive where
  • CaveAt least Cavern
  • Whole caveConfigurations: Backmount / twinset / Sidemount / CCR / Small cylinders / no-mount (speleo sumps)
  • Whole caveConfiguration unknown — research beforehand · doesn't decide who may dive
  • Whole caveGoes down to 45 m (trimix or deco may be needed) · doesn't decide who may dive
Depends on water level or swell

This is how the planner decides who in your team may dive this cave. Rules your own trip adds (organizer, a mail, the AI) show with your trip.

How to get there

By boat only, a long ride (>30 min) from Marseille (Pointe Rouge); south-east side of Riou, by the Impérial de Terre rock. Only in good weather.

Plan your route ↗

Around Grotte à corail de Riou (Impériaux)

Fills3 fill stations · nearest 0 km

  • Cassis Calanques Plongée

    ~6 min drive (estimate)

    Port de Cassis, 13260 Cassis

    Nitrox and trimix (tech and CCR courses); which gases visitors can have filled, and to what pressure: ask

    Open all year; ask for hours

    Dive centre with a boat at Cassis harbour (formerly Centre Cassidain de Plongée), inside the Parc national des Calanques; tech diving (trimix, rebreather) and CCR courses. Close to the Bestouan and Port-Miou. CCR support and sofnolime: ask.

    Website ↗Navigate ↗

  • Kraken Plongée (La Ciotat)

    ~16 min drive (estimate)

    Base nautique, Nouveau Port de Plaisance, Av. du Président Wilson, 13600 La Ciotat

    Air, nitrox, oxygen and helium; fills at 230 and 300 bar

    Ask

    CCR support: oxygen, booster and sorb

    The premises on rue Piroddi are temporarily closed; come to the base nautique in the Nouveau Port.

    Dive centre with a rEvo rebreather workshop and tech courses; two RIBs (7.5 and 6 m, 24 divers in total). CCR support: sorb (Sofnolime 797) in 20 kg drums or loose. Details confirmed by Kraken Plongée, Oct 2026.

    Website ↗Navigate ↗

  • Plongée Tek Marseille

    ~29 min drive (estimate)

    Port de la Pointe Rouge, 13008 Marseille

    Fills diluent (air, trimix) and O₂ for its own CCR and trimix students; fills for visitors: ask

    Ask

    Tech centre in Pointe Rouge harbour, the departure point for the Calanques and the Riou archipelago. CCR courses on rEvo, JJ-CCR, Shark, Triton and AP Inspiration; CCR trimix to -70 m. CCR and scooter rental: ask. Also +33 6 72 05 50 16.

    Website ↗Navigate ↗

Drive times from Cassis: we don't know this site's exact spot.

Caves nearby6

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Sources, sharing and disclaimer

Sources

Current conditions

Visibility, flow and water levels change quickly. Right before your dive, check what other divers report:

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Certification requirements, configurations and trimix depths are estimates for planning. Always check them locally and dive within your training. Compiled from web research (Parc national des Calanques, FFESSM/Subaqua 2013 and 2017, the Cassis – La Rivière Mystérieuse association, Wikipedia, Grottocenter/Grotto Map, Fontaine-de-Vaucluse commune, Préfecture maritime, DORIS, medsubhyp.fr, dive centres and dive-site databases; Sept 2026). The Trou du Diable, the Grotte de Gaméou and the Pointe Fauconnière are a tip from Kraken Plongée (Oct 2026). Pins from the park page, Grottocenter or Wikipedia (see each site); the Anse de Gaméou (also for the 3PP) and the Pointe Fauconnière approximately from OpenStreetMap; one site without a reliable pin; ~ = estimate. Rules change — check locally.