Tying Off in Current Without Losing the Job

By Ray Whitfield, ADCI-certified commercial dive supervisor. Reviewed by Amanda McCallister, editor.

Commercial Diving Contractors Alabama | Commercial Diving Contractors Alaska June 14th, 2019. The intake channel at the cooling water plant on Lake Michigan was running about 3,000 cfs. My tender had me on a 50-foot work line and we were trying to set a new flood gate seal. I told him to give me a little slack, and the next thing I knew the current had me pinned sideways against a trash rack grate. I couldn't move my arms. The only thing that saved me was the panic snap on my belt. That's when I stopped doing tie-offs by instinct and started doing them by the numbers. Tying off in current isn't a matter of strength. It's a matter of geometry and experience. The diver who ties off right can hold a position for an hour with one finger on the work point. The diver who gets it wrong is a hazard to himself and the whole team. These are the rules I've settled on after 28 years on inland and industrial jobs.

Read the water before you rig a single line

The first thing I do at any job site is stand on the bank or the deck and watch the water for ten minutes. Not the pretty parts; the ugly parts. I look for the eddy line where the fast water meets slack. I look for the foam circle over a submerged rock. I look for how the weeds lie over on a gravel bar. That tells me which way the current is going to push at the point I need to work. Most divers look at the surface and think they know current. But bottom current can be dead opposite the top in a deep channel. Especially at a dam, the boil can pull you down and the surface flow is just a show. If I can, I'll tie off a shot line and hang a few current meters at different depths, just to feel it. That's money well spent.

Anchor downstream, and let the current be your friend

The big mistake I see from newer divers is trying to tie off to the same structure they're working on, from the upstream side. That's how you get pinned. The current pushes you onto the object. If the object has any kind of grate or grate edge, your harness or your hoses get caught, and you are done. Instead, I anchor to something downstream or to a separate line that I can tend. For example, on a bridge pier, I'll run a line from the deck down to a point about twenty feet off the pier, then I'll clip into that line with a sliding hitch, so I can adjust my distance. The current presses me toward the pier, but the line stops me before contact. Then I just lean in and work. It sounds counterintuitive, but it's the safest way there is.

Set your angle to 45 degrees and not a hair less

Your tether angle to the current is everything. If you tie off parallel to the flow, the current swings you like a door. If you tie off perpendicular, it flattens you so much you can't lift your hands. The sweet spot is around 45 degrees. Then the current splits around you and you still have a good amount of lateral control. How do you get that angle? Use a short bottom line and a longer tag line. Or use a diagonal that runs from a downstream point to a point upstream. In practice, I'll often have two lines on my harness: one main tether and one safety line clipped to the upstream side of my harness so I can pull myself into the angle. It's a simple trick but it gives you a world of control.

Your releases have to work under load

The second thing I check before I get in the water, after my gas is open, is my release snap. I pull it with gloves on. I pull it with one hand. I pull it when the line is tight, by leaning away. If it doesn't release, I switch it out right then. Because I've seen too many divers hit the panic snap and it won't budge under pressure. Same with any sliding hitch. I use a prusik loop with a rated carabiner, and I test that it slides when I want it to and locks when I don't. In a bad current, you don't have the luxury of a free hand to mess with a jammed knot. So set it up right beforehand.

The countdown and the escape drill

Finally, be honest about what you're doing. Every job should have an exit plan that everyone on deck knows. If I get hung up on the intake gate, my tender knows to slave the line to a winch and take me off the negative. If I have a stuck strap, I can cut the webbing with a trauma hook on my chest. That's not a fallback; that's a plan. I've drilled this so many times, I can do it in the dark with heavy gloves. Once, on a job in a flash flood in the desert, I had to cut my work line and swim for my life. I got out because I had rehearsed the worst case. The tether was a smooth snap, not a knot. It took me about a second to drop it. Practice that. It's the most important skill you can have.

Frequently Asked Questions

What kind of line do you use for your tether in current? I use a low-stretch line like a 3-strand nylon or a high-tech splice, but really the key is a line that doesn't spin or curl. A lot of guys use a dedicated tether line with a snap at both ends. The diameter is less important than the visibility. I want a bright orange line so the tender can see it against dark water. How do you keep your lines from tangling on the bottom? Separate the work line from the tether. Keep the tether clipped to your harness when you're not using it, and keep the work line on a reel at the surface. The worst thing is a single line that does both. That's how you get a knot in the current. What's the most common mistake you see, even in experienced divers? They use too much gear. They have so many clips and carabiners that by the time they're in the water, they're a Christmas tree. Then something catches. I try to bring the simplest set-up that does the job. Less to snag, less to fail.