Searching for lost items in zero viz

Kirsty Andrews reports on a bizarre yet strangely fulfilling zero visibility diving experience with her club...

Henleaze swimming lake is a very picturesque former quarry in Bristol, where a local charity has run a swimming club since 1919. Bristol Number 3 dive club (also a venerable institution, being the third ever BSAC club, formed in 1953) has a good relationship with the lake trustees, and I recently paid my first ever visit to the lake with the club.

The peaceful and pretty venue, between 3 and 6 metres deep, attracts swimmers, divers of the non-scuba kind, and sunbathers optimistically soaking up the slightly-sub-tropical Bristol sun. It also makes an excellent spot for the dive club to practise various techniques, including refresher rescue training and Practical Rescue Management sessions. The visibility in particular (for more see below) makes for challenging search and recovery practice.

This latter activity is where the divers sometimes come in useful to the lake management. On occasion, valuable items are mislaid and the dive club can come to the rescue, putting our search patternsto use, and with luck, finding the missing item. Objects recovered over the years have included an electric chop saw and a

large marquee, which the trustees were particularly happy to recover!

Underwater, the lake is not as idyllic as above – there is a very silty bottom and the visibility on my dive varied from nil to a few centimetres. I conducted a quick search of the lake bed for obstructions around the newly renovated diving boards. When the main purpose of the activity is to trawl the lake bed, inevitably clouds of black mud and silt are disturbed, which doesn’t improve the situation.

I could just about make out the North arrow on my dive compass, but only if I lit it up with glowing absorbed light from my torch. Surface cover is crucial in managing this situation safely. One of the techniques we used was to place a line across the surface connecting the divers to the surface support: a tug from above indicates if it’s time to turn around or come up, and gives the divers some idea if they’ve veered off course.

It’s very disorientating to be underwater in these conditions, and even as an experienced diver it gave me pause when I first went in. Dives are short and of course can be stopped at any time. In a way though, these conditions inspire comfort - knowing that you can manage here means that you have experience to call on should you need it, for example if you lose visibility in a wreck penetration.

I was pleased to put my skills to the test and join in the fun, but my experience suggested that the lake bottom is pretty clear. My efforts only yielded a plastic bottle and a large piece of wood (medium-sized twig, according to my fellow divers) and another diver found a pair of swimming goggles. Still, from the perspective of reassuring the lake team, finding nothing much is just as good as finding something. I stayed relatively on course and only surfaced with a face-full of lake-side foliage once.

Several swimmers kindly thanked us for our efforts on their behalf (we went in just after closing time), and it occurred to me that this is one moment when diving is visible to the wider community. As a sport we tend to head out to our favourite coastal or inland spots which are well known to divers but otherwise quite separate from the wider world. It was nice to show non-divers what we do and introduce them to a little bit of the fun involved with our sport.