Avoiding entanglement

These days I often ascend from dives with litter for the rubbish bin. By October popular local shore dives and wrecks are festooned in fishing line. By the following spring the lines are all but gone, ripped away by the winter storms to drift around the ocean.

It was therefore deadly ironic that one day in 1991 I found myself at 47m tangled in mono filament fishing line. I have since had other close encounters of the entanglement kind including a shot line that was far too slack that got wrapped around my cylinder valve and turned it off as I descended (I swear I am not making this up).

How to avoid entanglement

1. A mask will cut your field of vision to about 90 degrees, so regularly scan above as well as around you, especially when diving wrecks or when drift diving.
2. Avoid the interior of wrecks and caverns unless you're trained to be there. The cylinder valves behind your head offer an obvious snag point so only ever swim under something with great caution.
3. Streamline your gear and keep critical items such as alternate air source, cutters, and BCD inflator close to hand around the chest area.
4. Avoid drift diving in poor vis and plan the dive so that you drift away from, rather than towards known risk factors such as wrecks and areas heavily fished with lobster pots.
5. Lobster pots are laid out in 'strings' with floating line used to link individual pots. As you swim past a lobster pot check that you have not swum under the rope linking the pots.
6. Shot lines should not be so slack in the water that they billow like a sail. They should be properly weighted, just long enough for the depth, and supported by at least 20kg of buoyancy.
7. Always keep a healthy reserve of air. For tech divers that may well mean doubling the amount of deco gas you think you'll need. A delay in leaving the bottom could drastically extend your decompression stops.

Tools for the Job:

We tried shears, a net cutter, a popular brand of BCD knife, and a conventional diving knife against a mono filament fishing net threaded with rope. Here's what we found:

1. Net Cutter. Pros: As the name suggests it slashed through mono filament line with ease but only if the line was in tension. Compact and easy to stow in a drysuit leg pouch or BCD pocket. Cons: Would not cut through rope very easily. Relies on the diver changing the blade frequently as they rust in sea water in a matter of weeks.
2. BCD Knife: Pros: This model featured a sharp serrated blade that was effective against rope. Small and compact with a neat attachment to the direct feed hose and a secure sheath that made deployment a doddle even when I was severely hampered by the net. Cons: not as good at dealing with mono filament as the net cutter. The handle did not have a good grip or hilt so did not feel secure in the hand whilst wearing thick gloves.
3. Shears: Pros: These medical shears will cut almost anything you can fit in the jaws. This was the fastest tool for dealing with both rope and net because lines could be cut whether or not they were tensioned. Easy to operate even with gloves on. Cons: cheap brands rust after a while (you can get a titanium coated version) but otherwise they're brilliant.
4. Diving Knife: Pros: This was a traditional style of knife that featured a straight blade on one edge and an incredible saw blade on the other that made very light work of thick rope as long as you could hold it in tension. The handle and hilt made it feel very secure. Cons: Bulky and difficult to stow without becoming a snag point. The straight edge seemed sharp but mono filament line easily slipped off the blade. The line had to be very tight before it could be cut.

We concluded that rather than carrying one cutter with a second as back up, two cutters should be chosen to compliment each other. My personal preference was for the traditional diving knife and the shears. However if you can only afford one cutter – the shears were excellent.

Dealing With Entanglement:

1. Stay calm.
2. Consider launching your delayed SMB to pinpoint your position.
3. Don't turn around to see what you have caught yourself on, this could cause further entanglement.
4. Maintain your posture and move backwards until you are either free or the line / net has been pulled taught. If the entanglement is behind your head consider slackening your BCD shoulder straps to gain improved reach.
5. If you need to use a cutter, retrieve it carefully so that you don't drop it.
6. Work slowly to locate the lines that you are caught in. You can gather them in one hand and cut with the other.
7. Given that most cutters work best on taught line, conventional wisdom is to make yourself positively buoyant to tension the lines. A conventional BCD makes this straightforward but the migration of air inside a drysuit or a 'wings' BCD can invert or rotate you into a posture that is difficult to correct whilst ensnared.
8. Slipping out of your gear to sort out entanglement may sound viable but with twin sets or weight integrated BCDs you may not be wearing much if any lead around your waist. In a buoyant suit you can then become inverted and possibly lose contact with your air supply.
9. It is clear that your buddy's assistance will be invaluable. If you are that buddy approach the diver and give a clear stop signal and approach cautiously giving yourself time to look for the best lines to cut.