Current events, Part 3: Swept away

In the previous two posts I talked about currents in the ocean, and how much fun it can be for divers to ride currents. While drift dives can be wonderful, diving in currents also can create situations ranging from nuisances to something bordering on terror. This is especially so when the currents are unexpected.

One kind of current we don't like to encounter while diving is the downcurrent. Divers need to be in control of their position in the water column, and there are few things more disconcerting than to suddenly feel yourself being pushed down unexpectedly by a mass of water.

We ran into this situation one time while diving off West Caicos, in the Turks and Caicos Islands. Most of the dives in the area are 'wall dives' -- that is, along the face of cliff-like dropoffs. In this case, the top of the dropoff begins at a depth of about 20 meters, and the base of the dropoff is something like 1,000 meters straight down.

The walls there are glorious -- completely encrusted with fans, sea whips, and large sponges of many colors. The wall is the underwater edge of the land, and there's nothing beyond but the open water -- deep and inky blue.

It's quite common to encounter large sharks, rays, and other pelagic fish during wall dives, which is a big part of why wall dives are so appealing. On the other hand, since there is no bottom to land on, or even to use as a reference point, buoyancy control is important. (And, I might add, you definitely don't want to drop anything!)

On this occasion, we were drifting along the wall nearly 30 meters under the surface. We were nearing what had been planned as the deepest point of our dive, so we were carefully minding our instruments for air consumption and depth. We noticed that just ahead there were clumps of bushy sea whips that were fluttering downward. I mean not just hanging downward, but fluttering as if water was being poured over them from above. (See photo.)

I paused to take a photo, and Jerry continued along ahead of me. When I looked away from the camera viewfinder and back at Jerry, I saw that he was not just ahead of me, but more than five meters below me as well -- and his bubbles were going down instead of rising up. He was in a downcurrent. As I watched, Jerry made a sharp turn straight out to sea and kicked hard into the blue. The maneuver worked and he escaped the downdraft, and circled back to the wall. We backtracked in the direction we'd come from rather than risk being pushed deeper again.

Some currents are more a nuisance than anything. We recently unearthed a certain batch of photos I had taken in the Red Sea, and had a good laugh recalling what it took to get the shots. It was during a shallow night dive in a sandy area with a lot of patch reefs -- an area we knew to be particularly rich in little critters of the sort that only emerge from their lairs after dark, so I set up my camera for macro photography. When we entered the water we noticed that there was a current that we hadn't expected, but since we had planned a shallow dive close to the boat, we continued.

We shined our lights around on the sand, and sure enough there were all kinds of interesting photo subjects, especially tiny things. That was the good news. The bad news was that the current sweeping across the sand grew in intensity over the course of the dive.

I spent most of that dive on my belly in the sand, sort of slithering along from one tiny subject to the next. As the current picked up, it wanted to flip me over, so Jerry spent most of the dive lying crosswise across my legs to hold me in place while I operated the camera. I'm sure that if anyone chanced upon us we would have made a really peculiar sight, and who knows what they would have thought we were doing! Really folks, it was just teamwork.

The picture at right is one result of our teamwork that night. You might have to click on the photo to enlarge it in order to see the teeny-tiny nearly transparent crab hiding at the base of the larger creature (called a sea pen - a relative of anemones).

Then there are the terror currents -- the ones that are not only unexpected, but so sudden and strong that they can sweep a diver away. The worst experience we ever had with one of those was at the Brothers Islands in the Red Sea, an area known for strong currents. The current we encountered there one July afternoon challenged us to the maximum.

Our boat had dropped all of the divers in our party along the fringe reef of Little Brother, the smaller of the two islands. The boat then continued to a mooring at the very tip of the island. The plan was for a one-way dive, meandering along the reef to where it ended, at the tip. It was one of those dreamy dives where everything was perfect -- the light was good, the visibility was excellent, the lush reef was spectacular, and there was no current.

Jerry and I were the lead pair of divers. The others were strung out behind us in twos and threes in a parade along the reef. At last we came to the tip of the island. Our boat and another were moored there. The other boat, let's call it #2, was moored close to the reef, having arrived there first, so ours was tied up at the mooring a bit offshore. We surfaced, identified our boat, and began to swim toward the boarding ladder at its stern.

As soon as we left the lee of the island we felt the current. We were swimming with our faces in the water, and just as we felt the current we spotted our boat's mooring line, stretched taught and actually vibrating in the current. We could see the bottom of the boarding ladder just below the surface, and underneath it the boat's propellers. The propellers were whirling as if the boat were underway, even though the engines were completely shut down, another indication of a rather strong current.

We barely had time to consider what we were seeing, because suddenly we felt like we were swimming upstream. The closer we got to the boat -- and the farther away from land -- the stronger the current. In less than a minute, we were making no headway at all.

We had begun our surface swim side by side, but since I had the bulky camera rig to push along I began to lose ground. I felt myself really beginning to huff and puff with exertion -- not a good sign. We were now less than 3 meters from the boarding ladder, but just couldn't make any headway at all, even though we are both strong swimmers. It was the most frustrating feeling.

Jerry made a few inordinately strong kicks and finally pulled ahead of me. A few more kicks like that and I saw his hand reach out and touch the ladder just as I ran out of steam and began to be swept backwards by the current.

It's funny how, in times like that, all of the training you've had clicks in and behavior switches to automatic. Realizing in a flash that I was not going to make it to the boat and that I was being swept away, I quit fighting the current, deflated my dive vest and dived under the surface. I let the current carry me nearer to boat #2, and I managed to dive deep enough to swim under the vessel. I surfaced again between that boat and the shore, again in the lee where there was no current.

I still had to solve the problem of how to get back to our boat, but at least I was no longer being swept out to sea. I called out and some of the crew of boat #2 looked over the side. I waved my arm. They waved back and hollered hello, thinking, I guess, that I was just being friendly. I called out again, and when a face appeared at the rail, this time I yelled "I need help." This time they listened while I told them about the current, and that I needed to get to our boat.

Meanwhile, Jerry had made it aboard our boat. The crew were below having lunch, and were unaware of what was happening until Jerry came aboard, breathless. His plan was to get out of his heavy gear, and re-enter the water to swim to me with a line that was tied to the boat at one end. The only trouble with that plan was that by the time he climbed on board and looked back, I was gone. He hadn't seen me duck under the surface, and he had no idea that I had managed to dive under the other boat and had made it to the lee side.

Then everything began to happen at once. The crew of boat #2 finally understood my plight. They threw me a line, and literally hauled me alongside and around their bow. They hailed our boat and heaved a line to the crew, ultimately attaching me to that line so that the crew could haul me across.

While that was happening, the next sets of divers in our party surfaced and started to swim toward our boat -- right into the current, of course, and they were as surprised by it as we had been. Jerry and the crew of our boat rushed to set a long 'current line' -- a strong line fastened to the boat's stern at one end, with a float at the other. One by one, the returning divers now swam to the current line, and one by one they got hauled to the boarding ladder.

The current line should have been set as soon as the boat tied up at the mooring. Why it was not was never explained to us. Nevertheless we all made it, camera gear and all. In order to use his arms to swim against the current, one of the divers did have to drop his camera. Fortunately it was attached to him with a lanyard, so he didn't lose it.

Speaking of cameras, when Jerry tells his version of this story, he likes to wait until someone asks what he was thinking when he turned around after boarding the boat and realized I was gone. He always answers, "I was just hoping she hadn't dropped that expensive camera!"

Current events, Part 2: Drift dives and thrill rides

In the previous post, I talked about the kinds of currents that divers encounter in the ocean. I ended with the statement that some currents are gentle, while others rip along with incredible force. Some of our most memorable dives have been in currents. Allow me to reminisce about some of the those.

After logging several thousand dives over a period of decades, as we have, you would think all those dives would blur together in memory. Indeed, some do -- yet many individual dives stand out clearly in our minds, almost as if we had done them yesterday.

Memorability often hinges on having seen something unusual or special -- a rare species, for example, or a first encounter with a big animal like a whale or a large shark. Memorability also is sealed by emotions felt during a dive, especially emotions that are fueled by an adrenalin surge.

Diving in currents often takes the form of a planned 'drift dive.' Divers enter into a known current, and ride it downstream. This is a very pleasant way to do some underwater sightseeing, because you can cover more territory with less effort. It's a lot fun -- as long as you have an exit point picked out downstream, or have a boat following your bubbles, ready to pick you up when you surface.

Drift diving in a mild current requires that divers still swim a bit, albeit with gentle assistance from the current. In a strong current, however, swimming is unnecessary. Instead the diver focuses on steering, mostly by using his fins as a combination rudder and dive plane. That's what Jerry is doing in the photo on this page.

If you look carefully at the photo, you'll notice that Jerry's bubbles are leading him (along with a trio of friendly jacks). The bubbles are being pushed ahead by a strong current that is also propelling Jerry, excusing him from having to kick.

The strongest current we have ever ridden as a planned drift dive was in a channel along the western edge of Bunaken, a small island off North Sulawesi, Indonesia. There, a drift dive in a very swift current became a high speed thrill ride. The current was so strong that we had to assume an unusual posture, just to keep from tumbling. Instead of facing down-current in a prone position, using fins for steering (as in the photo), we had to ride along sideways in an upright position, arms folded across the chest, with our legs straight down and crossed at the ankles, using our fins as a sort of keel for stability. We whizzed along so fast that taking photos was out of the question, but it sure was one heck of an exhilarating ride. We surfaced next to our chase boat whooping and cheering and high-fiving each other.

Currents sometimes run in layers. For example, an outgoing tide may create a current heading seaward, yet if there is a strong onshore wind, it may create a layer of surface current heading toward shore. Throw some underwater topography into the mix and even stranger things can happen.

One of the craziest dives we ever did involved multiple currents in multiple layers. When I say it was a crazy dive, I mean crazy in every sense of the word. The conditions sure were crazy, and maybe we were a little crazy for doing the dive, too, but I must admit we executed it just about perfectly. Let me see if I can explain.

We were on a live-aboard dive boat in the Red Sea, visiting dive sites near the the Sinai peninsula. Aboard the vessel were a small handful of relatively new divers, and another group of five very experienced divers with advanced training who were old hands at Red Sea diving. We were a part of the latter group. Because we were already very familiar with the dive sites there, and because we were all divemasters or instructors in our own right, we were left alone to manage our own dives, freeing the boat's lone dive guide to tend to the newbies.

Late one afternoon the boat brought us to Ras Mohammed, at the tip of the Sinai peninsula. Ras Mohammed is actually a complex of dive sites. The best known sites are just off the cape at the tip of the land peninsula, where a large pinnacle rises from the sea floor hundreds of meters down. At a depth of about 25 meters, the pinnacle splits into two, with a sort of plateau running between the pinnacles and then toward the land. The eastern pinnacle is known as Shark Reef, and the western one is called Jolanda Reef. Can you picture that layout?

As the boat approached Ras Mohammed, the two groups planned their respective dives. Expecting a bit of current running westward over the plateau, the dive guide planned to lead the 'baby divers' (as they were always called) along the eastern edge of the plateau to a site known as Anemone City. Our advanced group decided to enter the water at the same spot, but to drift with the current over the plateau, then swim between the two pinnacles and around the seaward side of Jolanda Reef, the more distant of the two pinnacles from our entry point.

We arranged for Armando, the boat's Italian deckhand, to pick us up in the boat's tender at a mooring buoy on the far side of Jolanda Reef exactly 50 minutes after we entered the water. Being a safety conscious lot, we even reviewed an alternative plan with the boat's crew, in case something should go wrong. We were all equipped with 'safety sausages' -- bright orange tubes (flattened, rolled up, and carried in our pockets) that turn into 6-foot high marker buoys when inflated at the surface. We showed them to the crew, telling them that if we could not make our rendezvous point for any reason, we would surface and inflate these markers, and wait for pick-up.

Our group entered the water first, followed by the baby divers and the guide. We immediately noticed that there was a surface current running in the opposite direction from what we had expected. The divers in our group signaled to one another to descend, and sure enough the current was running in the expected direction a few meters down. We pressed on.

By the time we got to the spot between the two pinnacles where we needed to make our turn to go around the seaward side of Jolanda the current was raging, but at least it was going in the right direction. Sort of. Because the current split at the pinnacle, the current was actually pulling toward the open sea at the side where we intended to pass. We needed to hug close to the pinnacle in order to round it, and we had to kick with all our might for a minute or two just to steer through the turbulence. Once we rounded the corner we had a free ride with the current again pushing us along effortlessly.

All of this took twenty minutes. We now had a half hour to kill before our pick-up. We poked along, back and forth across the face of the pinnacle, taking in the scenery and peeking into holes and on ledges as we ascended very, very gradually. As we approached 10 meters of depth, we encountered another current that pushed us seaward. We swam out of it in an arc, back toward the pinnacle, and again ended up in the pretty coral garden under the mooring buoy that was our target. Near the end of our allotted time now, we stayed there.

We heard the putter of the little outboard engine on the Zodiac as it approached. The deckhand shut off the motor and tied up to the mooring buoy just as the five of us popped our heads above the surface alongside the little rubber boat. Armando yelled as if he had seen a ghost, and blessed himself several times. As we hauled ourselves aboard, he kissed each one of us on the cheek. Clearly he was glad to see us!

Unbeknown to us, it turned out that the guide and the baby divers had aborted their dive after less than five minutes because they could not handle the surface current. The guide told the crew they had better start looking for us right away, because there was no way we would be able to make it to the mooring buoy as planned. They all had spent the past 45 minutes scanning the horizon, watching for our orange signal sausages, fearing we had been swept out to the open sea. They didn't see us, of course, because we had continued our dive as planned.

Armando had brought the Zodiac to the rendezvous point at the mooring buoy on schedule, but apparently hadn't really expected to see us. When we surfaced just when we said we would, just where we said we would, no one could believe it. When we got back to the boat everyone cheered. They treated us as if we really had been lost at sea and recovered, whereas the five of us felt we had simply "planned our dive, and dived our plan." Only in hindsight did we start to believe that maybe we had been a little crazy to continue in those crazy conditions.

Next time: A final episode on currents (at least for now).

Current events: Water that moves

Take a look at the photo on this page, and tell me: If you had to give it a one-word label, what would that be?

Non-divers might think something like 'pastels.' To a diver that photo screams current! That's 'current' as in moving water. [You can click on the photo for a larger view.]

Not only are the soft corals in the photo bending like wheat in a windswept field, but all the little fishies are facing in the same direction. That's what little fishies do in a current -- they point their little noses into the current and wiggle their tails for all they are worth, just to stay in place.

Good divers recognize and understand currents in the ocean, and know how to deal with them. The two most common factors relating to the kinds of currents that divers are likely to encounter are wind and tides.

Currents relatively close to the surface can be caused by wind blowing across the water. When wind blows across the surface it pushes a certain amount of water ahead of it. The stronger the wind, and the more open and unsheltered the surface, the stronger the surface current. Most wind-driven surface currents in coastal areas are only a meter or so deep -- a good thing to know. For instance, if there's a wind-driven surface current, a diver will probably have an easier time swimming back to a boat or a shoreline exit point by swimming a couple of meters beneath the surface instead of on the surface.

Some currents are caused by changing tides. The water mass flows toward shore during an incoming tide (called flood flow), and sucks back out to sea during an outgoing tide (called ebb flow).

Currents can be enhanced by underwater topography and the shape of a coastline. Think of the way water in a river or creek flows around rocks and other obstructions. The same thing happens underwater. If there is some relatively large feature in the path of the water mass during a tidal shift, for example, the water will flow around it and the current usually will be stronger and more turbulent closest to the obstruction. The same thing happens where there is a bottleneck -- a place where the flow of water gets squished between two large obstructions.

Currents encountered by divers most often move horizontally, but there are places and times where vertical currents are encountered. Upwellings occur when deeper water rises toward the surface. Downwellings occur in some places, too, but a more common type of downward current a diver may encounter happens where there is a dropoff of some sort. For example, a tidal ebb flow may literally spill over an underwater dropoff, just like a waterfall spills over a cliff on land.

Some currents are gentle, while others rip along with incredible force. Next time I'll tell you about some very interesting experiences we've had dealing with currents while diving.