Part II: The Ups and Downs of Ocean Currents

Different dive destinations have different types of currents. Protected as it is by Cuba, the Leeward Islands and Windward Islands, the Caribbean has few places with really strong currents. Maybe you've encountered wind-driven currents in Cozumel or Belize, but these pale into insignificance when compared with those driven by ocean tides.

Florida has a strong current, usually streaming south to north along its Atlantic coast, that is strong component of the Gulf Stream. Generally, these currents are constant in direction, if not strength, and you can enjoy taking advantage of drifting in them without getting lost or sucked under.

These Dive Sites Definitely Pull You In

You'll find very strong currents in the channels of tropical lagoons, where a very small difference in tidal height can make a huge difference to the torrent of water that pushes in and out. One notable destination includes the three channels of Aldabra Atoll in the Indian Ocean, where Cousteau once got his ship Calypso stuck in the flow of the main channel.

Then there are the passes of the Tua Motus in French Polynesia, where vast numbers of reef sharks aggregate in the fast-flowing water. Rangiroa has the second-largest lagoon in the world (Kwajalein in Micronesia holds the top rank). It has two broad channels, one being the Tiputa Pass, famous for a standing wave where dolphins regularly frolic when the tide is rising. Here, divers can get down and hook in with their reef hooks, being careful to latch on to secure substrate, and watch the show. When it's time to call the dive, divers release their hooks and allow themselves to be washed into the lagoon, ascending carefully as they do. These dives are only done safely on a rising tide when the flow goes into the lagoon. Nobody wants to get flushed out into the open ocean.

A gentle flow has to speed up when it passes over an obstruction. I remember well going down in the Bahamas with Stuart Cove to look at a wreck he'd just sunk. It had unfortunately turned turtle and was upside down on top of a reef wall, with its hull acting like an airplane's wing, and water was rushing over it. Cove rapidly discovered how useless were the new fins he'd just been given.

Similarly, although the currents in the northern Red Sea are generally benign, the tide flows round the southerly point of the Sinai Peninsula in such a way that divers simply have to choose to go with it. The only real hazard is getting accidentally washed up onto the top of the reefs.

In the Galapagos, the strong current at Darwin Island can be testified to by reader Christopher Watt (Needham, MA). "On a few dives, it was like being a flag being whipped by a strong wind, sometimes going hand-over-hand to get in position against the current. Good to use the shelter of large rocks or other formations to make moving around easier."

When he got separated from the group, Watt knew the right decision was to go with the [horizontal] current and not blow all his gas getting back to the group. He surfaced with his surface marker buoy and was spotted by the nearest Zodiac driver.

In springtime, monsoons bring strong currents and high-voltage marine life encounters to the most westerly atolls of the Maldives. The local diving dhoni drivers understand these inward ocean currents, squeeze around the thilas and kandus (sunken reefs), and always seem to know where divers are likely to surface.

Tidal currents are usually strong in Palau. Be aware that they can go both down and up as well as horizontally. Rose Mueller (Houston, TX) wrote, "We were in Palau during two of the most extreme tides of the year. My group wanted to go to Peleliu. The current was extremely strong and blew the other divers over the wall onto the shelf. We continued - and I suddenly realized I was 107 feet deep in a matter of seconds."

How to have a Safe (and Fun) Current Dive

Why dive where there are currents? Because it's where the fish are. If you can get to the "current point," the place where the current splits in different directions as it meets an underwater obstruction such as reef topography, you can find yourself comfortably in an eddy while watching the action.

Taking a ride with the flow can make for a relaxing dive, and you can cover a lot of ground as the seabed or reef rolls by. But currents cannot always be anticipated accurately. The late Larry Smith, an iconic dive guide in Indonesia, used to famously say in his dive briefings, "The current will be mild to wild," meaning you won't know until you get on the dive site.

But it's what you do when you surface that counts. You may have moved a long way from where you started. You need a very visible marker, either a tall surface marker buoy or a large flag on an extending pole that can be easily spotted above wave crests. I was once spotted several miles from my boat at Cocos Island, thanks to the flag I otherwise keep strapped to the side of my tank with elastic cord.

Once it becomes dusk, that emergency flashlight or strobe light you keep in your BC pocket proves invaluable. When a whole boatload of divers once went missing at Elphinstone Reef in the Red Sea, they were found by the aid of their lights after it got dark. In a worst-case scenario, a personal locator beacon might be a lifesaver.

Harry Pearson (Cape Canaveral, FL) tells of diving in strong currents at Malpelo, that lonely Colombian island out in the Pacific, back in the mid- 90s, and how a dive flag he deployed on an extending pole was very effective as a surface marker device to ensure he was later found by the pickup crew. Bowstone Diving in the UK supplies these flags, and ships them to the U.S. and Canada (www.bowstonediving.com). It's an inexpensive low-tech solution that is very effective.

Another one: a signal mirror. Peter Buzzacott, former director of injury monitoring and prevention at Divers Alert Network describes how to use it for signaling a boat. "Simply extend one arm and give a thumbs-up signal, lining up your thumb with the boat (or aircraft) that you want to signal. With your other hand, hold the mirror up to your eye and look through the hole in the middle at your thumb. Wiggle the mirror; when you see sunlight flash on your thumb, you'll know you are flashing at the boat or plane."

We often hold great faith that we'll get attention and be rescued due to the noise coming from whistles and those air horns driven by air from the diver's tank. However, people looking for you will usually be in a small boat, and it's difficult to hear anything over the noise of the engine. It's also a good idea to agree on a pre-arranged dive time so that pick-up boat drivers know when to expect you.

Similarly, a high-tech radio-driven solution is only useful if it's in working order, with its batteries charged, and your boat's crew know that you might use it and thus will listen for it on their radio receiver.

For more detail on safe current diving, take another look at "Diver Safety - It's Not Sexy!" in our November 2016 issues.

-- John Bantin