Underwater Navigation How To Use A SCUBA Compass

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Underwater Navigation: How to use a SCUBA Compass

The most commonly used SCUBA navigation device is the compass. All divers have one and should carry it with them whenever they descend into the abyss. We all know that there is no such thing as an underwater GPS for Divers! Unfortunately, many of us, including myself when I first started, do not really know how to correctly use the compass to navigate underwater.

The parts of the compass:
The Card:
This is the part of the compass that has the degrees and the letters that determine direction
The Bessel:
This a rotating piece of plastic on the outside of the compass which can be rotated to help us read our heading
The Lubber Line:
This line is fixed on the compass’ face and is used to help us read our heading.
The Side Window:
This is a window on the side of the compass that makes it easier for us to see our heading.
**Note that a digital compass does not have all these parts**

How to Use a Compass for Underwater Navigation
The first thing we need to go over is how to hold your compass when underwater. This is important because different compasses are mounted in different ways. Not knowing how to hold a compass can cause you to get an incorrect heading
Taking a heading
A heading is the number attached to the direction you are traveling in. It will always fall between 0 and 360 and is commonly known as degrees.
The Reciprocal course
This is a very common question. Because we take headings in a circle from 0 to 360 degrees, it is possible to calculate your reciprocal, or opposite heading. To do this we use something called the add subtract 180 rule. It requires a little math, but it is not difficult.
How to use your compass to assist in natural navigation.
It is a great idea to use your compass in conjunction with natural navigation. This is a very good way of avoiding tunnel vision, something that occurs when you are laser focused on your compass and you do not notice what is happening around you. I have seen it happen more than once that a student will focus so singularly on their compass that they will swim right passed the ascent line without even noticing it.
What if there is a cross current?
There are times when you will be swimming with a current coming across your body rather than in front or behind you. The idea here is to slightly deviate your swimming by slightly directing yourself into the current to compensate. Of course, this is not an exact science, but it will allow you to compensate for the current and get you closer to your destination.
I hope this has helped you understand the ins and outs of using a compass as a SCUBA navigation device. If you want to learn more all aspects of underwater navigation, you may be interested in b our course “SCUBA navigation mastered.” It provides a comprehensive course on all aspects of navigation. Click the link or the button below.

If you want more detailed information, check out our blog post by clicking the link below:

Underwater Navigation: How to use a SCUBA Compass

Don’t forget to download our free guide “The 8 Tools you Should Never Dive Without.”


In it, we go over several often-overlooked tools that you can use to navigate. Many of these tools are not reviewed by instructors so you definitely want to check it out.

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