From the srface, the tell-tale signs of a strong current are whirlpools interspersed with suspicious patches of calm
Get the most out of drift diving
This isn’t diving, it’s flying!” were the first words out of her mouth as she removed her regulator, eyes still wide and heart still pumping after an adrenaline-fuelled ride along a kilometre or more of Bali’s north-eastern coastline.
She had been carried along across a seabed teeming with life by the waters of the Indonesian Throughflow flooding the Lombok Strait on their way from the Pacific to the Indian Ocean.
This is drift-diving, letting the prevailing ocean current take command of the direction and speed of your dive.
The prospect of diving when a current is running is often a major source of diver anxiety. This concern is understandable, as a current puts the ocean firmly in charge, and many of us feel ill at ease when we are not in control of what is happening to us.
However, with the right skills and a little experience, dives when a current is running can be some of the best of your life.
Where and why?
The places where you will typically encounter current while scuba-diving include reef walls parallel to the shore, exposed and submerged seamounts in channels between islands, and passages through fringing reefs.
Quite apart from the excitement, the main reason you want to dive in places like this when there is a strong current is the fish! As water movement through channels and reef passages increases, everything comes in from the blue.
Huge schools start to congregate, clinging together close to reef walls and mid-ocean pinnacles for shelter. Then predators come in to feed on them. Seascapes that are quiet and relatively lifeless at times of calm water can turn into phenomenal action-filled aquatic circuses when the current picks up.
From the surface, the tell-tale signs of a strong current are whirlpools interspersed with suspicious patches of calm. A wavy line of calmer-than-usual water running parallel to the coast is a good indication that there is a current running along the shore.
Under water in the tropics, you know that a site is current-swept if there are plenty of gorgonian fans and sea whips there. The more water that moves past these corals and brings them nourishment, the larger they grow.
If you see them permanently bent like trees in a high wind, you know that currents there are often very strong.
Going with the flow
On a drift-dive, the best advice is to go with the flow, resist the instinctive urge to use your fins for anything more than balance, tuck your arms in and enjoy the ride.
The ability to anticipate, quick reactions and good control of your buoyancy and positioning in the water are useful qualities if you want to stay on course and avoid damaging either yourself or the reef.
A good drift-diver needs to be something of a slalom skier and know how to adjust speed and turn smoothly.
Make yourself as streamlined as possible and secure and tuck in all hoses and accessories, because you will be moving fast close to an uneven surface and you don’t want anything to get caught up as you pass.
Wear a full-length wetsuit with neoprene on your arms and legs to protect yourself from harm if you do brush against anything.
Follow the experts
To get the best idea of how the current is running, look at the fish. After all, they are the experts.
When there is no current, the fish, large and small, will be milling around all over the place.
In a mild current they will all be facing the same way, into the current, and the stronger the current becomes the closer to the reef they will go.
As the current increases in strength the little fish will be spread out flat and close to the coral, waving their tails like crazy to stay in position.
When it gets really strong they will be down in and among the coral structures, and even the big fish will be hovering very close to the reef.
If you want to take a break from the current during a drift-dive, use these big fish as your guide. You will find them behind large rocks or outcrops where they can shelter from the flow.
If you are a photographer, this is your opportunity to get up close, as they will be reluctant to move out of their hiding-place.
When you have found a hotspot on the reef or wall where there is lots of action, you will want to stick around and not allow the current to carry you away immediately. So you need to find a way of staying in place.
Finning like crazy against the current will tire you out quickly. Instead, you can grab hold of a solid bit of rock; first making sure that it really is a rock or, if you have one, you can deploy your reef anchor, also known as a current hook.
A reef anchor normally consists of one or two lengths of cord passed through the eye of a blunt-ended curved piece of stainless steel that looks like a large fishing-hook. A clip is attached to the other end of each cord.
The idea is that you wedge the hook into a crevice in a reef, snap the clip(s) on to your BC’s D-ring(s) and let go so that you can just hang in the current, held in place by the anchor, effortlessly enjoying the view.
Don’t be discouraged if you find it difficult at first to find your balance.
It may take a little practice over a few dives for you to become comfortable with the technique.
Going against the flow
Nobody enjoys swimming against a current. It saps your energy, increases your breathing rate, generates stress and is an experience best avoided.
However, sometimes you find yourself having to do it, at least in short bursts, as marine topography is not all straight lines and smooth curves. The reef line is made up of outcroppings, ridges and canyons that can deflect and reroute the current in unexpected directions.
There are techniques to make swimming against a current a little easier when it has to be done. Along a wall, stay close to the rock and use the contours to shelter you from the main thrust of the current wherever possible.
On a rocky seabed, you can use a cave-diving technique called “pull and glide”, reaching forward from stone to stone and using a single fin-kick to power each move.
Over sand, you can use a similar technique and walk with your fingers to help you sustain momentum and stop yourself going backwards.
Dealing with downdraughts and upwellings
Just the mention of a downcurrent is enough to inspire fear in many divers, as they visualise themselves getting caught by an irresistible force that drags them into the abyss with no opportunity for escape.
The natural response when confronted with a situation like this where you feel out of control is to panic, but there is no need.
Normally, downdraughts or downcurrents are localised phenomena that occur along reef walls: think of them as waterfalls in the sea.
When you encounter one, the first thing to do is get out of the flow by moving closer in to the wall so that its contours offer you shelter.
Once out of the stream, relax, exhale, take a few deep full breaths, check your air supply, depth and decompression status, look around you and plan.
Look to see where the big fish are hiding, or if there is a place where the sea-whips are not waving around.
It is not a good idea to fight a downcurrent. It is a struggle you cannot win. The oft-quoted tactic of inflating your BC to counteract its efforts to carry you down is potentially dangerous, because the current might suddenly release you from its hold and you will find yourself on a runaway ascent to the surface – which will do you much more harm than the current could do.
Unless you have spotted a place further along the wall that seems calm, usually the best advice is to swim laterally out away from the reef towards the blue.
If you find yourself being carried a little deeper initially, stay calm and keep swimming. Before long, you will emerge from the pull of the downcurrent and can return to a calmer section of the wall or begin your ascent.
Think of upwellings as reverse downcurrents. The same advice applies. First move into the wall out of the flow, relax, think, observe and act calmly.
Don’t get carried away
Because drift-dives can carry divers over long distances, loss at sea is a real risk, and it is essential that you choose the right operation with which to dive and are equipped to make it as easy as possible for the boat crew to find you at the end of your dive.
• Next month Simon Pridmore looks at Surface Safety and discusses what gear, techniques and strategies you should deploy to make sure your drift-dives always end well.
|Read more from Simon Pridmore in Scuba Confidential – An Insider’s Guide to Becoming a Better Diver and Scuba Professional – Insights into Sport Diver Training & Operations, both available on Amazon in a variety of formats |