Magnetic north needle: In the center of the compass is a needle (or an arrow printed on a disk) that is free to rotate inside the compass. This magnetic north needle, or compass needle, always points to magnetic north. By doing this, it creates an angle with the lubber line that you use to maintain a straight line as you swim.

Bezel: Most underwater compasses have a rotating bezel. To set the compass, align the two small, parallel index marks on the bezel over the compass needle. These help you maintain a straight direction of travel.

Heading References: Most underwater compasses numbers so you can record your heading (your direction of travel as measured in degrees from magnetic north). A few compasses have only general markings for north, south, east and west: you can use these for general navigation but for precision want one with degree headings.

Electronic compasses provide the same information and functions, but use digital readouts. See the manufacturer instructions if you're using an underwater electronic compass.

To navigate with a compass, the first step is to hold it correctly. Hold the compass so the lubber line aligns with the center line of your body. If you wear your compass on your wrist, hold the arm without the compass straight out and grasp it with your opposite hand near or above the elbow, solidly placing the compass rides in front of you. If your compass rides in front, hold the console squarely in front with both hands.

When using your compass, keep the lubber line aligned with Your body center line. Otherwise you won't swim along the lubber line, and you'll throw off your navigation even if you use the compass conrrectly other respects.