By Harry Averill
Dramatically improve your compass course accuracy
It’s been a long and relaxing dive. You and your buddies have gone from one coral head to another. You snap photos and marvel at the aquatic life. The catch is, your pressure gauges say it’s time to head back to the boat. Unfortunately, you’ve lost track of where you are.
The good news is, you are in very shallow water. Coming to the surface to take a compass heading on the boat won’t create the problems usually associated with bounce dives and sawtooth profiles. You surface and see the boat approximately 100 m/330 ft away. You take a heading on the boat so you can return on the bottom.
You and your teammates could swim back on the surface. But you remember your instructor telling you to avoid long surface swims when possible. Underwater, you avoid waves, strong surface currents, and boat traffic. You have plenty of air left, so returning to the boat underwater seems like the best option.
With your buddies in tow, you align the centerline of your compass with the centerline of your body and swim at a relaxed pace. You remember from your Advanced Adventures course you can expect to cover roughly 25 m/80 ft per minute at this pace. Your relaxed pace should get you back to the boat in four minutes.
Four minutes pass. You look up. No boat. Not even the shadow of the boat on the bottom.
You and your teammates surface. Looking around, you spot the boat 20 m/65 ft away. You elect to swim the rest of the way on the surface.
You’re frustrated, though. All the way back, you kept your eyes glued to the compass dial. You did your best to keep your body aligned with the compass’s centerline. What went wrong? And what can you do to prevent this from happening in the future?
Compass use has limits Underwater compasses work best over short distances. Why? Because no matter how carefully you try to keep your body aligned with the compass, you can still be off by more than 10 to 15 degrees. Several factors can affect this.
As the earlier example shows, over the length of a soccer or football field, these factors can cause you to miss your target by more than the length of a dive boat.
So what can you do?
There are several steps you can take to improve compass course accuracy.
Because the objects to which you are swimming can’t move, you can achieve close to 100 percent accuracy. It’s also a lot more fun than having your eyes constantly glued to the compass dial.
Things to remember Compasses can help you in several ways.