After learning about underwater navigation in their open-water class, many divers rely entirely on their divemaster or dive guide to point the way on every dive thereafter. But determining your location is a vital skill, both by using a compass and natural navigation underwater. In two previous articles, we addressed general ways to improve your navigation techniques as well as how to use a compass. Here, we’ll discuss how to use natural navigation underwater.
Using natural navigation underwater
Generally, as you begin to feel more comfortable and familiar with dive sites, you’ll start using natural navigation underwater. Distinctive features, visual references and clues from the surrounding environment will guide you successfully during the dive. As you know the dive site better, you may use your compass less.
If it’s an unfamiliar site, pay close attention during the briefing. During those 10 minutes the guide will share all the crucial aspects of the dive. He or she will probably mention key landmarks and features that can aid in natural navigation. Take notes on a slate if you need to. Which way is the reef? Will you swim back to the boat, or is it a drift dive? Use the opportunity to note details of any depths, hazards, or points of interest on the route, such as a significant pinnacle or outcropping.
In addition to the dive briefing, lots of other clues can help you use natural navigation underwater:
Waves and currents
The water movement will sometimes confirm that you’re heading in the right (or wrong) direction. In mild currents, the dive will usually begin by heading into the current. This makes life easier as, when you hit your agreed-upon turn point, the water movement will help you navigate back. If you’re in a sheltered part of the reef and unsure which way the current is heading, look at the reef edge for plankton floating in a particular direction. Also, most reef fish tend to hover nose-on to the current. This will help you decipher which way the water is running.
As we know, the sun always rises in the east and sets in the west. So, on a morning or afternoon dive, the direction of the sun — and the corresponding shadows — will help you gauge which way is which. The shadow of a dive boat moored above can also indicate where you are.
If you’re on a shore dive and your computer is showing increasing depth, there’s a good chance you’re heading away from the shore. Similarly, decreasing depth would usually indicate you’re heading back to the beach. If you’re looking for a wreck or pinnacle at 66 feet (20 m) and find yourself at 100 feet (30 m), you’ve probably taken a wrong turn. It may be time to abort the dive and head shallower.
Wildlife and topography
Make a mental note of any significant landmarks on the “out” leg of your dive. If there’s an outcropping featuring an impressive gorgonian fan, watch for it on the way back. Just like driving your car, landmarks can be reassurance and confirmation that you are heading in the right direction. On shore dives, the ripples in the sand that run parallel to the beach help guide you home.
Remember to listen. Noise such as crashing waves on the shore will give you clues as to where you are. Also, if you’re returning to a moored liveaboard dive boat, the buzzing of zodiacs and tenders above or, alternatively, the dull humming of the main boat’s generators can help determine where the vessel is.
Using a combination of general navigation techniques, compass navigation and natural navigation underwater, you should be able to find your way regardless of whether you’re diving only with a buddy or a group.