Diving in currents

In short

A current can make a dive superb, bringing life and clear water, or very tiring. You anticipate it using tide times, the weather and by watching the surface. On a fixed site, you start into the current and come back with it; on a drift dive, you let it carry you, together, under a surface marker buoy followed by the boat. Current increases effort and air consumption: knowing when to call or shorten a dive is part of diving. And at the surface, never fight it.

Why it matters

An unexpected current is exhausting: the diver fins hard, gets out of breath, uses air quickly and may end up far from the boat. Breathlessness is a common cause of incidents. On the other hand, a well-prepared current dive is safe and often spectacular. The difference lies in preparation, organisation and a few reflexes.

Where currents come from

• Tides: on tidal coasts, the water rises and falls, creating currents that change direction during the day. Their strength depends on the tidal range and the stage of the tide; they are often weaker around slack water, the short time when the current turns.
• Wind: a steady wind sets the surface layers in motion.
• Relief: points, passes, channels and shallows speed up the current; behind a rock, there may be none.
• Ocean currents: in some regions, they are always present.

Anticipating

• Check tide times and ranges and the marine weather forecast.
• Ask the dive centre or club: they know how the current behaves on their sites.
• Watch the surface: a buoy or moored boat aligned by the current, water streaming along the hull, eddies near points.
• Choose your time slot: many sites are dived at slack water.

On a fixed site: into the current, then with it

• Descend along the mooring line or a shot line, holding on so that you are not carried away during the descent.
• Start into the current: on the way out you are fresh and the cylinder is full; on the way back, the current carries you to the mooring.
• Shelter behind the relief: stay close to the bottom, in calm areas behind rocks, without grabbing living organisms.
• Set the turning point at the briefing, at a given pressure or time, with a wider margin than usual.
• Ascend along the mooring line if possible.

Drift diving

On a drift dive, you do not return to the starting point: the team lets the current carry it and the boat follows.

• Organisation with the boat: entry point and time, planned duration, surface signals, what to do if separated.
• Group entry and a quick descent to stay together.
• Surface marker buoy: often deployed by the guide for the whole dive, or at least for the ascent, so that the boat can follow the team.
• Tight team: stay within arm's reach of your buddy; in a current, divers lose sight of each other very quickly.
• Ascend together under the buoy, then wait together at the surface.

Effects on air and breathing

Finning against the current increases effort, and therefore air consumption and the risk of breathlessness.

• check your gauge more often;
• fin calmly and steadily; stop in a sheltered spot if you feel your breathing speed up;
• signal breathlessness to your buddy;
• call or shorten the dive if the current is stronger than expected: it is common sense, not a failure.

Swept away at the surface

• Inflate your BCD and stay calm.
• Signal your position: inflated buoy, whistle, horn, mirror or light; see the guide on surface communication.
• Do not fight the current: you would exhaust yourself. Stay together and let the boat come to you.
• If the shore is close, you can swim across the current to get out of it, without exhausting yourself.

Key takeaways

• Anticipate: tides, weather, local knowledge, watching the surface.
• On a fixed site, start into the current and come back with it.
• On a drift dive, stay together under a buoy followed by the boat.
• Current increases effort and air consumption: calling or shortening a dive is legitimate.
• At the surface, do not fight it: signal and wait for the boat.

Further reading

The safety accessories guide describes the surface marker buoy and reel; the air management guide explains how to plan a wider reserve; the types of diving guide presents drift diving among other practices.