Île Milliau Passage is a submersible channel connecting the mainland to the island, offering a distinct environment of sandy patches and dense kelp forests. Located 100 metres from the shore, this site is suitable for intermediate divers and provides a high-quality snorkelling experience. Depths range from 1 to 8 metres, with an average of 4 metres. Divers should be prepared for strong currents and surf conditions. Water temperatures fluctuate between 10C and 16C, with summer peaks reaching up to 19C. Wetsuits are recommended for all activities. Access is via shore entry, and parking is available nearby for visitors.

Baie des Pirates in Saint-Malo is a sheltered bay frequently utilised for snorkelling initiations. The site features shallow rocky reefs that provide a habitat for juvenile fish and various Atlantic algae. With water temperatures ranging from 10C to 17C throughout the year, the site is suitable for beginners. Access to the water is available from both the shore and by boat. Conditions at this location are variable, and it is recommended that snorkellers remain aware of the local environment while exploring the rocky topography.

Crique du Squeouel is a small creek located north of the port in Saint-Malo, France. The site features rocky walls that descend into sandy bottoms, providing a sheltered environment for snorkelling. Access is via the shore, and the site is best suited for intermediate snorkellers due to the variable conditions of the region. Water temperatures fluctuate between 10C and 17C throughout the year. Species recorded around this area include wrasses, European common cuttlefish, tompot blennies, sea stars, various crab species, soft corals, cod, spirographs, snails, sea squirts, and shannies.

Roche aux Serpents is an offshore rock formation located 500 metres from the shore near Saint-Malo. The site features a topography of deep gullies and swim-throughs, supporting a kelp forest environment. Divers and snorkellers can expect depths ranging from 5 to 18 metres, with an average depth of 4 metres. Access to the site is by boat only. Conditions include moderate currents and water temperatures typically between 10C and 14C, though seasonal variations may occur. The site is suitable for intermediate divers and offers a snorkel rating of 4 out of 5. Guided tours and local dive shop support are available for those visiting this area.

Molaine is a marine dive site located off the coast of Saint-Malo, France. The site features a consistent depth of 10 metres. Water temperatures in this area fluctuate throughout the year, ranging from 10C in March to 16C during the peak months of August and September. Due to the variable nature of the local marine environment, conditions at this site can change. It is suitable for divers looking for a shallow, consistent depth profile in the Brittany and Normandy region.

Île Molène near Trébeurden is a reef site accessible only by boat. The location is suited for advanced divers due to the presence of strong currents. Water temperatures range from 10C in March to 17C in August and September. Species recorded around this area include European common cuttlefish, wrasses, tompot blenny, soft coral, various crab species, cod, sea stars, spirograph, snails, sea squirts, and shanny. Facilities available in the region include dive shops providing air fills, equipment rental, and guided tours. The site is also rated for snorkelling.

Pors Mabo is a south-facing reef site located in Saint-Malo, France. This sheltered bay is known for its southern exposure, which provides relatively warmer conditions compared to surrounding areas. Snorkellers can explore the rocky edges of the bay, which offer a peaceful environment for beginners. Access is via a shore entry from the beach. Water temperatures range from 10C to 17C throughout the year, making the water cool for extended immersion. Facilities available at the site include parking, toilets, and a cafe. Due to the cool water temperatures, appropriate thermal protection is recommended for all in-water activities.

Pointe Du Corbeau in Saint-Malo is a reef dive site suitable for beginners. The site features a consistent average depth of 7 metres. Divers can access the reef via both shore and boat entries. Conditions at this location are subject to moderate currents, and the water temperature ranges from 10C to 16C throughout the year. Due to the temperate water conditions, appropriate thermal protection is recommended. Facilities available at the site include parking, toilets, and showers to assist with post-dive needs.