Reducing the guesswork.

The crew are quite visible but they’re not looking for you. In fact, they seem to be looking in the other direction; the direction of the dive site. You struggle to find your whistle but after a few minutes you feel seasick and try your DSMB (Delayed Surface Buoy Marker) instead. In the sloppy conditions you manage to half inflate it but it’s not really upright.
An hour goes by. You can barely see the boat but you think that it is now searching. Moving from side to side, they don’t seem to know where to look or in which direction to head. The net effect of wind and current running in different directions is difficult for the boat crew to determine visually, and since swimming towards them seems fruitless, your hopes sink with the sun. With no chance of being spotted for another 10 hours, your thoughts turn to survival, keeping warm and holding on. Not a situation anyone would want to find themselves in.

Real scenario

A few years ago I participated in a search for some divers in this exact scenario. They were found the next day after an air search costing well into six figures. I wondered for ages what could have been done by the boat crew to ‘know’ where to start looking immediately. How could they measure the effects of currents and waves and take the guesswork out of the equation? In 2007 I joined Mike Ball Dive Expeditions, a company that has always supported the idea of improving diver safety. I had been working on some ideas making use of buoys to track divers adrift at sea, and the company threw its full weight behind a series of experiments to determine the value of the concept.
In a typical drill we would mock up a fake human, dress it in dive gear and throw it in the water. After an hour the crew were alerted that we had a ‘lost diver’. They in turn would release a series of weighted lifejackets at set intervals and use them to create a ‘line’ on the sea surface.
After a few attempts, we managed to ballast the jackets with the right amount of weight so that they would mimic the actions of a surfaced, non-swimming diver. Once we got the balance between weight and flotation right, the results were astounding.

Developing a process

As we practiced it became apparent we could take the idea to another level. Instead of using multiple lifejackets, we could use just two or three purpose-built buoys and a little rudimentary mathematics to achieve the same aim, and with greater efficiency. We conducted weekly drills for more than a year and came up with a process that is both effective and simple.

Running the drill

First, once you suspect that divers are adrift, throw a buoy in at the point you assume they got lost. In most cases this will be at the dive site itself, especially if that site is in open water. Allow the buoy to drift for 10 minutes then launch a second buoy. Leave it for a further 10 minutes. While that is happening, try to get some indication when the divers got lost. This will depend on the situation but in general it’s easy to assume as divers and sites have idiosyncrasies specific to them. Other divers will be able to help with this. Ask around and come up with a figure in terms of minutes. If you can’t figure it out, assume they were lost from the time the dive started. Next, in the boat you intend to search in, drive between the buoys at a constant speed and time the run. Now divide the time the divers have been lost by 10 minutes which is the interval between when each buoy was launched. Multiply that figure by the time it took to traverse the distance between the buoys

As an example:

• Time assumed lost 60mins
  
• Interval between buoys 10 mins
  
• 60mins divided by 10 mins =6
  

If the timed boat run took 25 seconds, then multiply 25secs by 6, which equals 90secs. Then, keeping the buoys in line, drive at the same constant speed outward for 90 seconds. This is where you launch your third buoy, and in most cases you will have either passed your divers on the way out, or they will be near this point. You can then use this buoy as the basis from which to search as it should be moving constantly through the water at the same rate and direction as your lost divers

Making an early decisive move

The main value of the process is that it enables a boat operator to make an early decisive move, a move based on more than just guesswork. The key to its success is to use logic to determine the point where the divers were swept away from. In some complex current systems, this will require a cool head and a fair degree of local knowledge. Though it can’t be emphasised enough that the first priority in any lost diver situation should be to alert the local search and rescue authorities, in experienced hands, the use of buoys will allow a dive operator to initiate a logical search process, reducing the guesswork and considerably enhancing the chances of early success