Mark Hall Speights

“Downdraughts and Upwellings Just the mention of a downcurrent is enough to inspire fear in many divers as they visualize 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 localized 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 the 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 BCD to counteract its efforts to carry you down is potentially dangerous as 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, you will emerge from the pull of the downcurrent before long or its effect will weaken and allow you to begin your ascent and return to the wall. Think of upwellings as reverse down currents. The same advice applies. First move into the wall out of the flow, relax, think, observe and act calmly.”
― Simon Pridmore, Scuba Confidential - An Insider's Guide to Becoming a Better Diver