Discovering and respecting the underwater environment

In short

Diving well also means understanding the environment you are in: the sea, its tides and currents, its landscapes and the living things that inhabit it. A diver who can read a site dives more safely; a diver who knows how to observe sees far more; a diver with good buoyancy control who pays attention leaves the site intact for those who come next. This guide gives you the first landmarks.

Why it matters

The seabed is fragile. One fin kick can break in a second a sea fan that took decades to grow; an anchor can tear up a seagrass meadow; thousands of divers on the same site leave a mark. Divers are also privileged witnesses: their observations help scientists monitor the health of the seas. Knowing and respecting the environment means enjoying it for the long term.

Reading your dive site

• Tides: in the Atlantic and the English Channel, they change the water level by several metres and create strong currents. Divers often go in at slack water, the short moment when the current turns. Times are given in tide tables.
• Currents: they can change during the dive. If possible, start against the current so that you come back with it at the end of the dive, when you are more tired and have less air.
• Visibility: it depends on plankton, rain, swell and the type of bottom. Poor visibility means staying very close to your team.
• Temperature and thermocline: a thermocline is a sharp boundary between warm surface water and colder water below. You can feel it and sometimes see it (blurry water).
• Weather and swell: wind, swell and storms determine water entry, exit and the boat's safety. The dive supervisor decides whether to go ahead with or cancel the dive.

The main environments

• The Mediterranean: clear water, small tides, temperature varying with the seasons. Posidonia seagrass meadows, walls covered in sea fans, coralligenous reefs.
• The Atlantic and the English Channel: marked tides and currents, cooler water, very rich in life (seaweed, kelp, crustaceans, sponges).
• Tropical seas: warm water, coral reefs, a great diversity of colourful fish.
• Lakes and quarries: fresh water, often cold at depth, variable visibility, specific fauna (pike, perch, crayfish).

Some remarkable ecosystems

• Posidonia meadows: posidonia is a flowering plant (not seaweed) found only in the Mediterranean. Its meadows shelter many species, produce oxygen and protect beaches from erosion. They are protected and grow very slowly.
• Coralligenous reefs: a landscape built by calcareous algae and fixed animals (sea fans, sponges, bryozoans) on Mediterranean walls. Very rich, it is also very fragile.
• Coral reefs: built by tiny animals, polyps. They host exceptional biodiversity and are threatened by warming water.
• Wrecks: quickly colonised by fixed organisms and fish, they become true artificial reefs.

Observing fauna and flora

• Where to look: in crevices and under overhangs (a torch helps, even by day), on the sand (many animals hide there), in open water (schools of fish) and in seagrass meadows.
• How: approach slowly, without sudden movements, keeping your distance. Breathe out gently: bubbles scare some animals away. Stay still for a moment and life comes back.
• Understanding behaviour: a fish facing you may be defending its territory or its eggs; an octopus changing colour is signalling its state. The rule is to observe without disturbing.

Protected species

Some species are protected by law: collecting them, and sometimes disturbing them, is forbidden. In the Mediterranean this is the case, for example, for the noble pen shell, the dusky grouper and posidonia. Lists change and depend on the country: ask your club or check the French national natural heritage inventory (INPN).

Species to know for your safety

Few animals are dangerous to an attentive diver, but some sting or burn:

• Weever fish and scorpionfish: fish with venomous spines, often resting on or buried in the bottom. Watch where you put your hands and knees.
• Jellyfish, Portuguese man o' war and some hydroids: their stinging tentacles cause burns.
• Lionfish: beautiful, but with venomous spines; it is also an invasive species in some regions.
• Sea urchins: their spines break off in the skin.
• Moray eels: they are not aggressive if left alone; do not put your hand into a hole.

If you are stung or burned, tell your instructors, get out of the water and follow first-aid instructions; seek medical advice if the pain is severe, if you feel unwell or if you have a general reaction.

Eco-friendly diving

• Work on your buoyancy: it is the most important environmental skill. A well-balanced diver does not touch the bottom.
• Control your finning: keep your fins off the bottom, use gentle kicks, avoid stirring up the sand.
• Do not touch, feed or take anything: no animals, plants or shells, even empty ones, and no objects from wrecks.
• Secure your hoses and accessories so they do not drag on the bottom.
• Mooring: use mooring buoys where they exist; never drop anchor in a seagrass meadow.
• Sun protection: prefer UV-protective clothing to sunscreen, some ingredients of which harm the environment.
• Respect marine protected areas and their rules (no-go zones, seasons, diver quotas).
• Follow the responsible diver charters offered by federations and associations.
• Bring your rubbish back, and even rubbish you find, if it is safe to do so.

Never hold on to coral or a sea fan to fight the current. If you need to, place one finger on bare rock, after checking that no animal is hiding there.

Contributing to citizen science

Your observations are valuable. Citizen science programmes collect divers' photos and reports: rare or invasive species, the state of seagrass meadows, strandings, litter. The French federation, for example, runs DORIS, a collaborative encyclopaedia of underwater fauna and flora, and its biology committees organise surveys. Record the place, date and depth of your observations: this is the most useful information.

Key takeaways

• Check the tide, current, visibility and weather before diving.
• Approach marine life slowly and observe without touching.
• Good buoyancy control is the best thing you can do for the environment.
• Do not feed or take anything, and respect marine protected areas.
• Share your observations with citizen science.

Further reading

The app helps you identify the fish you photograph and offers a species catalogue. Shared observations feed a map and the biology guide, and can help improve species recognition. The useful links guide lists the main naturalist resources.