Intermediate 8 minutes
Navigating with a compass: headings, reciprocals, and patterns
The instrument is simple; what usually fails is how you hold it
The dive compass has no electronics, rarely fails, and costs little. And yet, most wrong headings underwater don't come from a faulty instrument: they come from holding it crooked.
In this article you'll see the parts of a dive compass, how to hold it correctly, how to set and return along a reciprocal heading, and the two basic navigation patterns.
The compass solves exactly what natural orientation can't: holding a precise direction when there are no visual references, or when you need to get back to a specific point.
The parts and the posture
A dive compass has a capsule filled with liquid that dampens the movement of the magnetic disc, a lubber line marked on the housing that indicates the direction of travel, and a rotating bezel with two reference marks that lets you set a heading without having to remember the number.
Correct posture is what decides whether the instrument works or not. Three conditions at once: the compass must be horizontal, so the disc can turn freely; the lubber line must point exactly where your body is facing; and you have to turn your whole body to change heading, not just your wrist.
That last point is the most widespread mistake. If you turn the compass until the heading lines up but your body is still pointing somewhere else, you'll swim in a direction different from what the instrument shows, and the error accumulates with every meter.
The practical way to guarantee alignment is to hold the compass with both hands, elbows tucked against your body or resting on your chest. That way the instrument stays locked to your torso and can't drift out of alignment on its own.
One detail worth noting: nearby metal objects and electronic equipment can distort the reading. It's a good idea to keep the compass away from your tank, torch, and dive computer when taking a heading.
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