Provence · about 2 km from Cassis
Exsurgence de Port-Miou
- Max depth233 m
- CertificationFull cave
- Water temperature≈ ~16 °Cestimated, no reports yet
- SpecialDPV-suitable
Diving and fills
Dive here with
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Fills nearby
- Fill stationCassis Calanques PlongéeNitrox and trimix (tech and CCR courses); which gases visitors can have filled, and to what pressure: askRoute ↗
- Fill stationKraken Plongée (La Ciotat)Air, nitrox, oxygen and helium; fills at 230 and 300 barRoute ↗
- Fill stationPlongée Tek MarseilleFills diluent (air, trimix) and O₂ for its own CCR and trimix students; fills for visitors: askRoute ↗
What it looks like
CASSIS CCR cave dive Port Miou, Le Bestouan Plongée souterraine Port Miou #plongée #diving #cavediving Port Miou CCR Dive 2017 plongée port miou du bord et du barrage
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Videos and posts
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CASSIS CCR cave dive Port Miou, Le Bestouan Plongée souterraine Port Miou #plongée #diving #cavediving Port Miou CCR Dive 2017 plongée port miou du bord et du barrage
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Other people's footage, not advice: how someone else dives here says nothing about what suits your team. Dive within your training.
The dive
At the entrance there is a halocline with a cloudy layer. The floor is fluid clay throughout: divers can reduce the visibility to zero. The water is ~16 °C and brackish, because seawater penetrates deep into the system.
Profile and sections
At the entrance there is a halocline with a cloudy layer. The floor is fluid clay throughout: divers can reduce the visibility to zero. The water is ~16 °C and brackish, because seawater penetrates deep into the system. There is cave fauna (molluscs, crustaceans); at the entrance you see fan mussels and spirographs.
Port-Miou is Cassis's largest submarine spring: on average ~7 m³/s, ranging from 3 to 100 m³/s; at low water there is hardly any current. The dam (1972–1976, 530 m from the sea) was meant to keep the salt out for drinking water, but the water stayed brackish. Surveys and measurements are by the Cassis – La Rivière Mystérieuse association.
- Depth and profile
- S1 530 m / -25 (average -20 m) to the dam ('cloche 530') · S2 2,450 m / -223, mostly between -6 and -40 m up to the terminal shaft; air bell at 1,475 m · depth record -233 m (2016, horizontal passage below the shaft) · total ~3.5 km
- Configuration
- All configurations in the huge main passage (200–400 m² cross-section). On open circuit at least a twin 15 l set (FFESSM). The deep explorations beyond the dam use CCR (trimix 6/82), bailout and scooters.
- DPV: DPV-suitable
- Long, roomy passage: scooters are used for the explorations beyond the dam. Up to the dam (530 m) there is little to gain.
Who can dive where
- At least Full cave
- Configurations: Backmount / twinset / Sidemount / CCR / Small cylinders / no-mount (speleo sumps)
- Goes down to 233 m (trimix or deco may be needed)
- Experienced divers only
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
Sea entrance in the Calanque de Port-Miou: two entrances ~20 m apart; the spring emerges at ~-10/-12 m. Park on the Port-Miou peninsula, take the stairs by the tennis courts behind the tunnel and enter from the small beach; ~150 m swim (bearing ~260°). The calanque is a municipal mooring zone with heavy boat traffic; according to a dive-site database you may only dive there with special permission — ask the harbour office beforehand (+33 4 42 01 96 24, VHF 9). Beyond the dam, explorers enter through an artificial ~45 m shaft by the hut in the calanque (ladder, gear lowered by winch). It is not open to visitors: only through the FFESSM discovery days or the research association.
Around Exsurgence de Port-Miou
Fills3 fill stations · nearest 2 km
Cassis Calanques Plongée
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.
Kraken Plongée (La Ciotat)
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.
Plongée Tek Marseille
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.
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