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February 2023    Download the Entire Issue (PDF) Vol. 49, No. 2   RSS Feed for Undercurrent Issues
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Cozumel Diver Disappears from Surface

what you need to know about down currents

from the February, 2023 issue of Undercurrent   Subscribe Now

The rise and fall of the tide, no matter how imperceptible to us, can cause a big pressure difference between an ocean and a smaller sea or lagoon, becoming apparent when the water flow confronts reefs, walls, or other underwater obstructions. Like the air passing over an aircraft's wing, the water has to speed up to pass an obstacle such as a submerged reef. For example, the slight tidal difference between the Pacific Ocean and the Rangiroa Lagoon in French Polynesia can produce a spectacular standing wave as it passes through the constricted Tiputa Pass.

Downward currents can be strong, multi-directional, and dangerous. They can begin the moment a tide changes

The Danger of Down Currents

Currents can also be caused by strong wind or high-pressure atmospheric conditions building up pressure in the open ocean. When a current comes up against a vertical wall, it must flow up and over, around, or down. That vertical down current can be very dangerous to those divers unaware of how to cope.

Divers meet down currents at the Maldivian atolls' outside reefs and at Indonesian islands, where there is a tidal difference between the Indian Ocean and the smaller seas to the north, such as the Banda Sea. Indonesia's Raja Ampat is well known for its currents. One of its famous sites, Cape Kri in the Dampier Strait, often has an infamous down current that may appear just as divers are finishing their dives. It can whisk divers down to 130 feet before releasing them to bob back to the surface, a frightening experience for an unsuspecting diver. Divers have died there.

They Can Be Very Localized.

Downward currents can be strong, multi-directional, and dangerous. They can begin the moment a tide changes. There may be tell-tale signs: schooling fish swimming energetically yet vertically, or soft corals flattened in the flow.

Sometimes they are very localized. The flow that promises to send you down 100 feet might not affect a diver only a few feet away from you. In my early diving days, I had the surreal experience of trying to climb a reef wall near Komodo when another diver kindly offered me his gloves. He was not affected by the current and was wondering what I was doing, yet he was only an arm's length away.

Swim horizontally away from whatever is causing the down current, usually a reef wall.

If you find yourself in a down current, it can be of little use to inflate your BC or SMB or to try to swim up against the current. I've watched in awe as the surface marker buoy I deployed at 60 feet hit the down current near the surface, turned away from the reef face, and descended fully inflated.

Imagine a Waterfall

Think of a down current as a waterfall. If you get close to the wall, you might get out of it in the lee of an overhang. But where do you go? Certainly not rock climbing. And you're not a powerful swimmer like a salmon.

So, you must swim horizontally as hard as you can away from whatever is causing the current - that waterfall - to flow downward. It's usually a reef wall. You don't know how wide the waterfall is, so swim toward the open ocean and out of the waterfall.

If you did inflate your BC and dropped your weights, you risk an uncontrolled ascent to the surface once you are free of the current - so that's to be done only if you are almost out of air and totally out of ideas.

That Cozumel Death

It was an unfortunate American diver who found himself in such a down current during a dive at Santa Rosa reef on the south side of Cozumel on January 16. Frank Szat (Itasca, IL) was aboard the same boat as the missing diver and posted this on Facebook:

"My wife and I were diving on the same boat, different dive group. The 'lost' diver was very experienced. He was only several feet from his wife and his divemaster on the wall as they were preparing their SMB. A sudden down current pulled him down before anyone could help. The currents were strong and multi-directional, but manageable the whole dive ... up until that point . . . . There was even a vortex at the surface over blue water as we came up from our safety stop."

He was diving with Dressel Divers, who according to another Facebook poster, Jacques Le Brock (Montreal, Quebec), responded as best they could. "I was on the boat and witnessed it all. They had to account for the other divers/teams while preparing to search. I am confident they did not delay the search, and they did not 'lose him.' The dive master and his wife were within sight when it happened. The divemasters and dive company did everything they could."

That afternoon, personnel from the Naval Search, Rescue, and Maritime Surveillance Station began to look for the missing diver after he failed to resurface. He has not been located.

The current was so localized and instant that his wife and a dive guide were less affected by it. Even though he was an experienced diver, he couldn't respond quickly or correctly and disappeared into the depths. What a terrible tragedy for his wife to witness.

We reviewed scores of Facebook posts regarding this incident, and it was apparent that many Cozumel divers who posted knew nothing about down currents, having never been told about them either in certification courses or by Cozumel dive operators before a dive.

Cozumel down currents occur frequently. I don't recall how many divers Undercurrent has reported have disappeared in Cozumel's down currents over the years, but I may have run out of fingers to keep counting.

But don't be put off by the prospect of down currents or any currents. Just be prepared. The small amount of rising tide at the constriction of the Tiputa Pass into Rangiroa's Lagoon is so powerful it forms a standing wave, yet Stan Waterman dived the pass when he was 80 years old.

You can too.

- John Bantin

Here are some links to read a few past articles.

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