At sea, the general rule is to use a 7x magnification, because the movement of the boat will make any higher magnification difficult to use. The magnification is the first number that you'll see on the binocular packaging. The second number refers to the size of the objective lens, which is the lens at the end of the binocular. For most marine functions, a 50mm lens is sufficient, so the standard marine binocular is 7x50.

Practicality is also a big issue. Try to get a pair of rubber coated binoculars, as these will stand up to more wear and tear, and will provide you with a better grip in wet conditions. Some will come with a central focusing unit, while others, particularly the waterproof variety, will have individual focusing on each eye piece. There are also some that can be set to a -1 diopter mark, which is a standard setting for most normal sighted people. This eliminates the need for re-focusing every time you pass the binoculars around which can be very beneficial if you are in a hurry or working in stormy conditions. Additionally, these fixed-focus binoculars can also be easier to waterproof since they have fewer moving parts.

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