Who doesn’t enjoy the thrill of feeling like you are flying while being pushed over a reef by a moderate to strong underwater current? Diving in a current can be exhilarating and fun but could lead to a problem situation if you are not vigilant.
Currents are caused by a number of factors including the tides, wind and thermally unstable water columns. Usually currents run in a horizontal direction, parallel to the earth’s surface. These are perfect for doing a drift dive. There are, however, certain situations that could create currents to run vertically up (up currents) or down (down currents) while in other situations underwater currents can create a horizontal vortex. If a diver gets caught in one of these currents it might lead to a problem situation fast.
Down current
A down current occurs when a current hits the face of a wall or when it runs at a right angle to a drop off. They can also be formed where two currents that are moving in opposite directions meet or move over each other.
Down currents are dangerous because they can pull you deeper than your planned depth. Sometimes this can occur gradually, without you realising it until you feel the need to equalise, or look at your depth gauge or dive computer. In some situations a down current can pull you from 5 meters down to 20 in a few seconds.
Most down currents will become weaker lower down, don’t just sit back and wait for the ride to end, though as there is no telling how deep this will happen.
If you get caught in a down current: Stop. Think. And then Act. Stay calm and maintain a natural breathing rate to try to conserve air. Swim out into the blue, I realise that this might be scary but down currents generally become weaker further away from the wall or drop off. While you are swimming out, you also want to swim up – aim at swimming up at a 45° angle.
If the current is especially strong you might want to inflate your BCD. An inflated BCD creates a larger surface area for the current to push against, thus it might not help as much as one might think. If you inflate your BCD, be ready to deflate it rapidly once you are out of the current to avoid a run-away ascent. Avoid dropping your weights unless you absolutely have to.
Another option is to get as close to the wall as you can. You can ‘climb up’ the wall. The current is likely to be at its strongest here and you might need to hold on to corral in order to pull yourself up. If you decide to use this option, do so with caution and try to keep yourself and the corral as safe as possible. Try to hold on to dead corral and avoid stinging hydroids.
Up current
Similarly to down currents, up currents can occur when a current hits the face of a wall. Up currents are dangerous because they can pull you up to the surface very quickly. This rapid ascend could possibly lead to Decompression Sickness, or even a lung over expansion injury or Arterial Gas Embolism.
Like with a down current the best thing to do is swim away from the wall or drop off, into the blue. Swim down and deflate your BCD.
Washing machine
A washing machine current occur when currents get ‘bounced’ around by the bottom typography. Washing machine currents can leave you feeling very disorientated as you get pushed in all directions. This disorientation can be amplified when your bubbles get swirled around; making it very difficult to tell which way is up. As with up- and down currents, try to swim out of the current horizontally while swimming slightly against the push of the water to avoid drastic changes in your depth.
Vortex
Very little information is available about these currents and they only occur at a few dive sites around the world. The best way to deal with this kind of current is to avoid getting caught in them all together. If you do get caught in one, try to conserve as much energy, wait until you feel it weakening slightly and swim perpendicularly out of it.
Here is a video that shows how easily a diver can get caught in a vortex. Note the horizontal ‘snake’ of bubbles that can act as an early warning that this kind of current is present.
How do you recognise these kinds of currents?
Strong currents, horizontal or vertical, can often be predicted by looking at the surface of the water. Areas where the surface is choppy in the absence of a moderate to strong wind, mixed with areas of very smooth water could indicate a strong current. If the boat that you are diving from is tied to a mooring buoy, look at the direction in which the boat is turned. If the boat is tied off at the bow, the boat will be facing into the direction from which the current is coming. If the mooring line is tight, the current is likely to be moderate to strong.
Underwater you can tell which way the current is going by looking around you. Soft corral will sway in the direction in which the current is travelling. Fish face into the current, so if you see a school of fish pointing in one direction, that is the direction in which the current is coming. If you look at a school of smaller fish and they are swimming around freely in different directions, there might only be a slight current or even no current at all.
Bubbles can also tell you a lot about the current. Strong down currents can sweep your bubbles into the depths, as can horizontal currents. One of the only ways to identify a vortex is by its distinctive serpent-like horizontal ‘river of swirling bubbles.
Diving in currents can be fun and safe if you stay vigilant and practice good judgment. As with any other dive if you feel uncomfortable or not up for it, rather cancel or abort your dive and move to a dive site with slightly less extreme conditions.
*A version of this article first appeared at www.scubadiverlife.com
