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Hi all A number of folks asked me for more detail on underwater orienteering, so here it is. Underwater orienteering appears to have arisen spontaneously in several countries during the Sixties, apparently as a result of military divers taking their work (underwater nav. exercises) home with them. Since then it has become a sport with formalised rules and regular international competitions which are administered by CMAS (the world underwater federation - largely unheard of in the USA). An orienteering course consists of 5-10 buoys laid out in a lake to form a course with a length of 600-700 m. Competitors are equipped with scuba gear and a navigation rig which consists of a very accurate compass and a distance meter. The competitors must navigate around the course, either finding each buoy in sequence, or rounding them in some pre-arranged order (depending on whether it is a "finding" or "rounding" course). Points are awarded for each buoy found or rounded, and for speed in finishing the course. Courses are typically laid out in water of 5-15m depth, but most swimmers swim at a fairly shallow depth (2-3m) because the visibility is generally better at shallow depths. Each competitor tows a surface marker buoy for safety (in lieu of a buddy) and so that the judges, who are on the surface, can see how the competitor is progressing. The navigation is fairly straightforward. Compass courses and distances are worked out from a scale map of the course, which is prepared beforehand. The swimming accuracy required is very high; it is necessary to swim with an error of less than a degree, and distance error of less than 1% in order to have a reasonable chance of finding the buoys in bad visibility without searching. In the event that the buoy is not found, one can of course search, but this is time-consuming and leads to poor scores. The compasses used are usually yachting compasses, and distance meters are usually home-made affairs consisting of a small propellor which turns in the water flow and drives a small mechanical counter (such as the counter used in cassette players to show how many feet of tape have been played). Interestingly, nav rigs of this kind were used to speed up the mappping of the deeper reaches of the Drachenhauchloch underground lake in Namibia, so there is some connection to caving here. Certainly, both activities seem to attract the same kind of diver; the kind happiest when in pea-soup visibility. While orienteering is a fun activity for ordinary divers at club level, particularly for people condemned to inland diving in boring waters, it has become a fiercly competitive sport at international level; and it is hardly recognisable as diving at this level. It was adopted with enthusiasm by most of the Eastern Bloc countries in the bad old days when sport was idealogical war, and so a disproportionate amount of time and effort went into what is after all a very fringe activity. Until very recently, most of these countries had de facto professional teams, and their domination can be measured by the fact that the highest placed western country at the last world championships was Germany, who came 6th (and whose team consisted almost exclusively of ex-GDR folks). For serious competitors nowadays, the standard equipment is a 6-7 litre aluminium tank (steel tanks affect the compass) which is built into a streamlined fairing that is pushed in front of the swimmer so that a flat, streamlined attitude can be achieved. Ordinary fins have given way to monofins (a large single bladed fin with two foot pockets which is used for dolphin kicking) and the masks used are simple moulded perspex shells which give complete (albeit distorted) peripheral vision. Using this set- up, the top competitors achieve speeds through the water of 2m/s, and up to 3m/s in short bursts. These top folks are still almost full- time sportspeople (the women's category is as competitive as the mens') - mostly navy personnel or students on sports scholarships. It takes a stack of training to swim 650m in 5 mins, with a total accumulated error of one or two meters after that distance. For those of us doomed to working for a living, its still possible to reach a level where one can go to the World Championships (held in Europe in even years) or the World Cup (a sort of European League in which competitions are held in different European countries on one weekend of each month of summer) without being laughed at. (I hope so anyway; maybe they laugh at us when our backs are turned). Why? Because swimming as fast as you can, underwater, in zero visibility, while trying to keep a compass needle rock steady, is peculiarly addictive. (Yes, I keep this activity a secret from my professional colleagues...) Anyone wants still more detail, e-mail me again. Countries which have active orienteering fraternities are France, Germany, Italy, South Africa, Russia, Estonia, Sweden, Kazakhstan (current world champs), Slovenia, Slovakia, Austria, Hungary, Czech Republic, Poland....Ireland, Colombia, Zimbabwe and Egypt compete fitfully. I'll probably get flamed by someone I forgot. Oh well. Safe diving Jon
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