Compass
Compasses are made in a variety of shapes and sizes; though, they all are built based on the same principles.
Typically, a magnetized dial, or compass card is placed onto one or more pivot points in a container filled with fluid. This allows the dial to move freely in a circular motion, as well as tilt marginally from side-to-side and back-to-front. Underwater compasses also benefit from the fluid, as it helps support the overall integrity of the compass due to increased hydrostatic pressure under water.
The dial’s markings are subdivided into 360° degrees with the four cardinal points; N at 0° degrees, E at 90° degrees, S at 180° degrees, and W at 270° degrees clearly marked.
The dial is magnetized so that the North cardinal point aligns with the Earth’s magnetic north. On the outside of the compass is a rotating bezel marked from zero to 360° degrees, typically with significant indicators at the zero and 180 degree positions. There is a static, straight line on the compass, called the sighting line, or lubber line, which is typically used in-line with the direction of travel.
Many underwater compasses have a viewport on the side facing the diver that indicates the diver’s direction of travel, or bearing.
Compasses built for diving may be wrist mounted, slate mounted or console mounted. However, wrist mounted compasses are typically more versatile, and easier to use, providing better navigational results.
Other Instruments for underwater navigation
In addition to the traditional compasses, the electronic underwater compass is also very popular, a navigation tool made with the most modern technologies, that can be used both in and out of the water.
This tool can display headings corrections to the course you want to maintain, store the different routes taken during a dive, and reconstruct the routes to determine which direction to take to be able to return to the starting point.
Divers who wish to use the electronic compass that modern “high-end” dive computers are often equipped with, should carefully read the instructions provided by the manufacturer before using them underwater.