Basic underwater navigation by means of simple observation or use of a compass and depth gauge remains a fundamental and essential skill for all divers. For most short excursions, these are the only instruments needed. Even when using advanced navigation instruments, basic navigation skills provide an important backup.
Much navigation can be accomplished by observing the environment. This is called natural navigation. Note the depth at the start of the dive along with the composition of the sea floor (rocky, sandy, etc.). Note important underwater landmarks such as boulders, big coral heads, patches of kelp and similar objects. Make a mental note of the time taken to swim from one landmark to the next. Notice the direction of the current. A basic knowledge of underwater features will help as well. For example, wave ripples in the sand typically run parallel to the shore and the sea floor normally slopes up toward the shore.
More precise navigation and even some basic measurements are possible by using a compass and watch. The diver starts by taking a compass bearing, then holding the compass in a horizontal position in front of him (note that compasses are prone to jamming if not kept horizontal). Be aware that metal items and dive instruments close to the compass may cause an incorrect compass reading.
(Source: NOAA Diving Manual: Diving for Science and Technology, 5th Edition; 2013, Best Publishing Company)
NOAA Diving Manual, 5th Edition
Used by divers everwhere, the NOAA Diving Manual 5th Edition is the most comprehensive resource for learning about dive equipment, dive planning, decompression, and emergency medical care of an injured diver. Chapters also include more advanced concepts such as physics and physiology, mixed gas diving, surface-supplied diving, saturation diving, and the list goes on.
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