Specialty dives: night, wreck, cave, ice, altitude

In short

Some dives require particular skills, equipment and organisation: night dives, wrecks, caves, ice and cold water, altitude. Each offers a unique experience, and each has its own risks. This guide presents, for each type, its appeal, its risks, the equipment and the recommended training. It expands on the types of diving guide; some environments, such as caves, require specific training.

Why it matters

These dives add a difficulty to usual diving: darkness, a ceiling overhead, intense cold, different decompression parameters. Divers who attempt them unprepared face situations they cannot manage. Well prepared and approached gradually, they are among the finest dives.

Night diving

• Appeal: marine life changes completely: sleeping fish, crustaceans, cephalopods, bioluminescent plankton.
• Risks: team separation, disorientation, light failure, difficulty being spotted at the surface.
• Equipment: primary light, backup light, a light marker on each diver, sometimes a light on the boat or mooring.
• Organisation: preferably a site known by day, a simple route, agreed light signals, smaller teams.
• Training: often a supervised dive or a dedicated qualification, depending on the agency.

See the guide on surface and night communication.

Wreck diving

• Appeal: history, atmosphere and abundant attached marine life.
• Penetration or not: staying outside the wreck is an ordinary dive; entering it means an overhead environment (no vertical exit, collapse, silt that destroys visibility) and requires specific training, a guide line and suitable equipment.
• Risks: snagging, cuts on metal plates, fishing lines and nets, navigation, depth.
• Equipment: light, line cutter, surface marker buoy.
• Respecting the site: a wreck is often a place of remembrance, sometimes a grave. In France, maritime cultural property is protected by the Heritage Code: removing objects is forbidden and any discovery must be reported to the authorities. Touch nothing and bring nothing up.

Cave diving

• Appeal: unique landscapes, often very clear water.
• Risks: a permanent overhead environment, losing the guideline, loss of visibility through silt, light or gas failure far from the exit. It is one of the most demanding environments in diving.
• Equipment: guideline, several lights, gas redundancy, suitable configuration.
• Training: specific training is mandatory, step by step, with specialised instructors. Never follow a line into a cave without this training, even for a few metres.

Ice and cold-water diving

• Appeal: special light under the ice, very clear water, cold-water marine life.
• Risks: intense cold, regulator freezing that can cause a free flow, an overhead environment under the ice, hypothermia at the surface.
• Equipment: regulators suitable for cold water, two independent first stages on a twin-outlet valve, dry suit, thick gloves and hood.
• Surface safety: marked hole in the ice, diver tethered to the surface by a line held by a team, protection from the cold between dives.
• Training: specific qualification and experienced supervision.

In very cold weather, avoid breathing from the regulator out of the water and limit use of the purge button, both of which encourage freezing.

Altitude and lake diving

• Appeal: mountain lakes, clear water, different landscapes.
• What changes: atmospheric pressure is lower at altitude. The ascent to the surface therefore represents a larger relative pressure change, and decompression parameters must be adapted: altitude tables or a computer set for, or compatible with, altitude. The drive up into the mountains before the dive also counts.
• Fresh water: less dense than sea water, it requires less weight and slightly changes the depth reading, depending on the instrument.
• Other risks: often cold water, even in summer, and visibility that drops near the bottom.
• Training: altitude diving qualification or training, depending on the agency.

See also the guide on flying and altitude, for going to altitude after a dive at sea.

Key takeaways

• Night: primary light, backup light, light marker and agreed signals.
• Wreck: do not enter without training, remove nothing.
• Cave: specific training is mandatory, never follow a line without it.
• Ice and cold water: suitable, redundant regulators and a surface team.
• Altitude: adapted decompression parameters and compatible instruments.

Further reading

The app's watch calculates decompression for diving at sea level; its MN90 and Bühlmann models do not support altitude: do not use it to plan a mountain lake dive. The guides on types of diving, navigation, night communication and technical diving complement this one.