LEVEL UP YOUR SKILLS AND EXPONENTIALLY EXPAND YOUR DIVING ADVENTURES
Text by DAN World’s Safety Services Team
Of all the obstacles a diver can encounter, currents can be one of the most underestimated and physically demanding. Even experienced divers sometimes seem unable to accurately assess the speed and impact of a current. Currents can accelerate your air consumption and exhaust you, and can even make it impossible for you to return to your dive boat.
Water is 800 times denser than air, so it creates a resistance that is magnitudes stronger than the resistance caused by even a storm-level wind. At half a knot, divers hanging on an ascent line will feel their bodies moving into a horizontal position, much like a flag in a 10-mile-per-hour breeze. At currents approaching a knot, turning your head to the side can dislodge and flood your mask. Letting go of an ascent line in a two-knot current even for a brief instant can mean being swept away.
CURRENTS ARE UNPREDICTABLE
Divers should be aware that currents do not necessarily travel in one direction at any given time. Tidal currents, for instance, can reverse direction during the dive, and it is not unusual to have surface currents change speed or direction midwater.
A detailed dive briefing should always precede a dive involving currents. It will orient you to the possibilities you’ll encounter, and provide the protocols for dealing with them. Before you go too far into your dive, stop and use a visual or physical reference, like an anchor line, during the descent to help you judge the strength of the current and how it will affect your dive. Diving in a current requires one of two strategies – you can either choose to go with the flow or against it.
UNDERSTANDING CURRENTS
Before you consider diving in a current, it’s important to have a basic understanding of how they work, especially as currents can vary in intensity as you descend through the water column. As a general rule, currents closer to the surface and in midwater are stronger than currents at the bottom. Just as you can stand behind a building to block a cold wind, the contour of objects at the bottom slows the flow of water. For example, putting yourself between a large shipwreck and a current can prevent you from being swept away by it. In addition, even small reef structures can significantly slow the water’s speed.
DRIFT DIVING
Going with the flow, or drift diving, is an extremely relaxing way to dive. It is important to stay with your group, so that the “bubblewatchers” can track you from the surface. Regardless, you should have a visual and audible signalling device with you on every dive to aid in surface recovery. In addition, the boat crew should provide you with detailed instructions for exiting the water.
If you’re doing a drift dive from the shore, the protocols are similar. However, instead of a boat captain, you’ll need to arrange shore support, such as a car to pick you up at a pre-arranged rendezvous point. You’ll also have to plan how you will exit the water with your dive buddy.
WORKING AGAINST THE FLOW
Swimming against even a mild current is physically taxing. It depletes your air supply more quickly and can even accelerate gas loading, which is a concern as it relates to the risk of getting decompression sickness (DCS). In strong currents, dive boats often deploy current lines. Holding onto it provides an effortless wait for a buddy or when waiting your turn to reboard after your dive.
Effective current swimming requires three steps:
Gear preparation
Your dive gear should be streamlined with no dangling items. Even an extended regulator hose or a dangling console can create drag.
Proper weighting
Divers tend to add more weight to descend quickly in strong currents. But the added weight makes it difficult to achieve a streamlined position in the water at depth. It takes practice, experience and knowing your gear to have proper weighting for a current dive. Practise negative descents (totally deflating your BCD before you hit the water) in mild currents first. You might have to fin against the current to reach the dive site, but at least you won’t be overweighted at depth.
Position
Both the position of your body and your position in the water column are important. Stay neutrally buoyant as soon as you meet the required depth and avoid contact with the reef.
USE YOUR SIGNALLING DEVICES
If you are down current from the boat, and the current is too strong to swim against, don’t fight it. Get positively buoyant, dumping weight if necessary, and inflate your surface marker buoy (SMB) as soon as possible. If you have to make a safety stop during your ascent, inflate your SMB from below the surface. This will alert the boat crew to your location and they can track you while you are off-gassing.
Having a signalling device, such as an SMB, is essential, so that your boat can spot you easily if you have drifted away with a current
Complement the visual signal with an audible one, like a whistle or air horn, a device that is attached to the inflator hose, and continue to signal the crew until you are sure they have seen you. The crew may have other divers to pick up before they can come to you, so stay calm, keep your mask and snorkel in place, and maintain eye contact with the boat. If you are with your buddy, stay together.
Complement the visual signal with an audible one, like a whistle or air horn
EXPAND YOUR SITES
Knowing how to dive in a current exponentially expands the number of sites you can dive, and confidence in your skills makes each dive a safer, more enjoyable adventure. Before you jump into the current, get some training in the skills you’ll need, practise them in a controlled environment, and expand your experiences slowly as your comfort level grows.
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