If appropriately planned for and sensibly executed, diving in these conditions can be hugely rewarding, often exhilarating, and even relaxing when going with the flow. But diving in current can also be stressful, and, if not prepared, divers can easily find themselves in dangerous situations.
The risks of diving in strong current can include rapid air depletion, separation, accelerated gas loading, severe headaches and increased susceptibility to DCI. It’s important to know what to expect, and how to prevent risks from becoming reality. Here are a few tips on how to deal with strong currents so that you can make the most of your experience the next time you decide to enter the fray.
Planning and Briefing
One of the most essential steps for creating a positive dive in strong current is planning. This includes understanding the type of current you may encounter, listening closely to the briefing before a dive and making sure that all members of the group know what to do if things go wrong. A comprehensive dive briefing should be given and strictly adhered to, detailing how the group will descend and ascend, how any issues will be dealt with, and what can be expected throughout the dive. It is important that divers know what to do in case of separation, since this is one of the most common problems of diving in strong current and happens most frequently during descent and ascent.
Decide If You’re Going With or Against the Current
Especially when dealing with exceptionally strong currents, it is advisable to conduct your dive as a drift dive in order to preserve energy. It is imperative that the boat is able to follow your progress in order to provide support and a pickup at the end of the dive, so the dive leader should carry either an SMB or a delayed SMB, and it would be wise for each member of the group to also carry a delayed SMB in case of separation. To ensure that the boat is able to find you once you have resurfaced, it is also a good idea to carry either an audible or a visual signaling device (i.e. a whistle or dive mirror). If you find yourself separated from the group on a drift dive, surface at a safe speed but without delay — the further away from the group, and therefore the boat, you will drift the longer you spend underwater. Those diving with a delayed SMB should deploy them on beginning the ascent to give surface support a head start on locating your position.
If a drift dive is not possible, always begin the dive swimming against the current; swim back to the ascent point with the current is easier for tired divers. Plan your dive carefully according to the speed of the current, and choose a turn-around point with divers’ air consumption rate in mind. A good rule of thumb is to turn around once a third of your air supply has been used.
Keep Low, Get Streamlined and Weight Correctly
As a general rule, most currents are stronger at the surface and in mid-water. When swimming against a current keep close to the seafloor, where the shape of the reef breaks the current’s flow and causes it to slow. Sometimes it’s possible to find temporary shelter from a strong current in the lee of large objects, like coral outcrops, pinnacles or shipwrecks. Streamlining one’s gear is also an important part of diving in strong current; dangling gauges and accessories cause unnecessary drag, and can cause a dangerous situation if they become entangled while moving over the reef at speed.
It is important that divers are correctly weighted when diving in strong current; too little and a quick descent can become impossible, while being over-weighted can hinder streamlining and efficient swimming position once underwater. In order to conserve energy while swimming in current, divers should aim to maintain a horizontal position in the water, minimizing the resistance of the oncoming current.
Decide What Gear to Take
Inexperienced divers should consider leaving unnecessary items like large underwater cameras, video cameras and torches behind when diving strong currents for the first time. These items not only interfere with buoyancy and cause additional drag, but trying to operate them while also dealing with the current can lead to additional stress and even panic via task-loading.
On the other hand, there are several pieces of equipment that may not be part of your regular kit that can greatly ease the stresses created by strong currents. In addition to the compulsory surface marker device (whether an SMB or a delayed SMB), divers may choose to equip themselves with a reef hook or a buddy line to prevent separation. The former piece of equipment allows divers to attach themselves to the reef via a blunt hook wedged in a rock crevice or similar cavity, stopping their progress and allowing them to wait for other divers, catch their breath or keep their hands free for taking photos. However, it is important that the reef hook is only used in areas where there is no coral, or where the coral is already dead. Dive boats may have a tag line, which extends from the boat’s stern and allows divers to hold on while waiting to exit the water after ascent.
Because diving in currents can be strenuous, it is important to check your gauges with more regularity than you might on a normal dive. Swimming against a current can lead to overexertion, and therefore significantly increase your air consumption.
Similarly, if you’re caught in a down current, keep a constant eye on your depth, and when the current releases you, on your ascent rate. You cannot fight a down current — remain calm and wait for it to level out. Inflate your BCD to counter the current’s downwards pull, but be prepared to let air out immediately once you are free of it to prevent a rapid and uncontrolled ascent.
Be wary of swimming too close to the shallows when in strong current, especially near a rocky outcropping, pinnacle, reef wall or wreck. The current will be especially strong here and you may find yourself suddenly caught by an upwelling and unable to stop your ascent. In this situation, dump the air from your BCD immediately (remembering to use your dump valves if not in a vertical position) and grab hold of the reef or rock if possible.
When being dropped at a site where you know there are currents, ask your skipper to drop you a sufficient distance upstream from the mark. This distance will depend on how long it takes your group to descend — if you do not do this, you will have missed the site completely by the time you reach the seafloor. In strong current, it is often best to enter the water negatively, allowing for a rapid descent and minimizing the chances of separation at the surface.
Above all, remember that diving in currents can provide the most thrilling, rewarding dives of your life. Be prepared, remain calm and never hesitate to abort the dive if the conditions are too much, but most of all remember to have fun.