Night Diving: A Beginner's Guide to the Underwater After Dark

Night Diving: A Beginner's Guide to the Underwater After Dark

The first time you night dive, it is almost certainly more surprising than it is frightening. You descend with your torch beam illuminating a narrow cone of reef, and the reef looks nothing like it did this afternoon. The coral polyps are extended — white, translucent tentacles fully deployed to catch passing plankton. Things are moving. Things are hunting. Things are enormous.

Night diving is one of the most rewarding specialties in recreational scuba, and it is significantly less technically demanding than most divers assume before they try it.

Why Dive at Night?

The short answer: different animals, different behaviours. Most of the reef's hunters are nocturnal.

• Moray eels leave their holes and actively patrol the reef
• Octopus emerge and hunt crabs, flashing iridescent colour changes as they move
• Spanish dancer nudibranchs — some of the largest and most spectacular — only appear after dark
• Crustaceans (lobsters, crabs, shrimps) come out of hiding; bioluminescent ostracods flash blue-green as they spawn
• Hunting whitetip reef sharks work the reef in coordinated groups, poking into crevices for sleeping fish
• Sleeping parrotfish can be found motionless in mucous cocoons they secrete each evening
• Plankton bioluminescence — wave your hand slowly and watch the blue-green sparks streak away from your fingers

Equipment

You need a primary torch and a backup torch. Most dive operations require this combination for safety.

• Primary: 500–1,000 lumens minimum; rechargeable or C/D cell battery; wide and focused beam modes are both useful
• Backup: Any small torch that works; clip it to your BCD where you can reach it one-handed
• Dive light signals: Know them before the dive. A slow circle means OK; rapid circles mean 'attention/problem'. Never shine a light in another diver's eyes.
• Glow sticks or tail lights: Clip one to your cylinder valve so your buddy can see you from behind

How to Navigate

Begin with a site you've dived in daylight. Know the entry and exit points. Many night divers use a surface marker buoy (SMB) on ascent. Follow the reef contour rather than swimming in open water.

If you get disoriented, go up — not to the surface, but ascend slowly and look for your buddy's light and the surface glow of your boat. Boats at anchor should have a dive light deployed in the water as a reference point.

What Not to Do

• Don't panic if something swims through your torch beam. Barracuda and sharks are curious about light and will investigate — this is normal. They're not hunting you.
• Don't shine your torch at sleeping fish. You can approach within centimetres of a sleeping parrotfish without waking it, but a direct torch beam will startle it and ruin the observation.
• Don't separate from your buddy. The standard buddy rule applies; it applies more strictly at night.

The Best Sites for Night Diving

• USAT Liberty, Tulamben (Bali): Spanish dancers, moray eels, nudibranchs — the wreck transforms completely
• Koh Tao, Thailand: Shallow, calm, predictable — ideal for first night dives
• Bonaire shore dives: The entire coastline is accessible; Salt Pier at night is outstanding
• Lembeh Strait (Indonesia): Night muck diving — the critter capital after dark
• Heron Island (Australia): Coral spawning events; hunting whitetips; loggerhead turtles on the beach