You must be able to accurately determine the distances you travel under water in order to complete underwater routes. To be successful, you need to propel yourself at a constant rate and consider the effect that currents have on your position.
Two methods that can be used to calculate distances while under water are:
Distances covered per fin cycle
Distance underwater is calculated by determining the distance you cover per fin cycle. A fin cycle is when both legs have moved completely up and down.
If you are conducting a reciprocal course and you count 20 fin cycles on the way out, then you should count 20 fin cycles on the return heading. If you are conducting a square pattern, each side should be the same amount of fin cycles.
In actuality, you will need to maintain the same force per cycle throughout the route and may be faced with slight currents. If this is the case, you may have to kick more or less intensely than you did on previous legs of the route. If the current pushes you sideways, you will need to take corrective action to stay on course.
Distance over time
To calculate distance over time, you use a timer to determine how long it takes you to travel a known distance.
For example, if you travel in a direction for 2 minutes and 20 seconds and wish to return to the starting point you will travel the reciprocal route for the same amount of time, 2 minutes and 20 seconds, applying the same fin cycle force.
For this method to be accurate, you must use a timer, and kick consistently, with the same amount of force for each kick cycle. As before, be aware of currents and the affect they may have on your position.
Once you’ve learned how to properly operate an underwater compass and calculate distances, you will find yourself using underwater navigation more with each dive.
Underwater navigation can be an enjoyable game and a challenge that grows into a passion for many divers. Mastering underwater navigation will also greatly assist you when diving in limited visibility water, and increase your overall enjoyment of the sport.