How To Choose Binoculars For Boating (Best UK Guide)

How To Choose Binoculars For Boating (Best UK Guide)

Whether you’re a day sailor, a yachtsman, a kayaker or a passenger on a cruise ship, a decent pair of marine binoculars will help to improve your enjoyment. Plus if you skipper a boat a good quality pair of marine binoculars will be invaluable for navigational purposes. In this article we’ll cover all you need to find the perfect pair of binoculars for all of your nautical needs.

Many of the companies manufacturing marine binoculars nowadays have many years of experience working with the Naval authorities of many of the world’s top navies. The technological advancements they have made have been shared with their commercial teams to produce the very best in marine binoculars.

What Magnification Is Best For Marine Binoculars?

Marine or boating binoculars shouldn’t have a higher magnification than 7x because of the rolling motion of the boat, any higher than 7x will be too shaky to be of any use. This allows the objects to appear larger without them moving too much to see.

What’s The Correct Objective Lens Size For Boating Binoculars?

As you should be aware, the size of the objective lens determines just how bright the image appears through the lens. The objective lens size also has a lot to do with the overall weight of the binoculars too. With that in mind we recommend an objective lens of 50mm for boating binoculars.

To discover the magnification and the objective lens size, just look at the body of the binoculars, there will be a set of numbers stamped upon it somewhere. They’ll look something like 7×50 which indicates 7 times (X) magnification and an objective lens diameter of 50mm.

Field Of View

It seems odd to be talking about a field on water, but it’s just the technical term for how much you can see through the binoculars from left to right (or in this case port to starboard) without moving your head. The larger field of view you have the better, especially if you’re spotting for obstacles, reefs or islands etc. In general terms an angular field of view of 6° to 8° is acceptable for binoculars.

That’s a linear field of view of 315 feet per 1,000 yards to 394 feet per 1,000 yards or 105 metres per 1,000 metres to 140 metres per 1,000 metres depending which system you use. To convert degrees to feet just multiply the degrees by 52.5 and to convert to metres multiply the degrees by 17.5 because 1° is equal to 52.5 feet or 17.5 metres.

Eye Relief

When you look at the specifications for marine binoculars you will see the term eye relief, it’s referring to the distance between the eyepiece and the eye for maximum field of view. The eye relief is usually given in millimeters and is commonly between 13 and 16mm. For those of us that wear glasses there are binoculars with long eye relief usually 16 to 24mm to allow comfortable room for the glasses and still see the full field of view.


All marine binoculars should be waterproofed, they should also have an IPX code of 6 or above. IPX7 is even better as this allows for them to be submerged in a metre of water for at least 30 minutes without ingress. This degree of waterproofing should also keep any dust, sand or other undesirable objects out too.

Floating Strap

As well as waterproofing, it’s a good idea to consider investing in a floating strap. For the sake of around £15.00 the floating strap fits over the original binoculars strap and prevents the binoculars from sinking which will make it easier to retrieve them from the water.

There are some marine binoculars that actually float! In which case a floating strap will be unnecessary but the majority are not buoyant so we would advise investing in a floating strap. 

Fog Proofing

Fog proofing is achieved by removing the air from the lens tubes and replacing it with either argon or nitrogen which has no moisture content. This means it cannot react with fluctuating temperatures and will not fog up. Which is very useful when leaving the warm cabin to stand on deck and look for marker buoys.

Protective Coating

Marine binoculars or binoculars for boating in general should have a protective coating to prevent damage whilst on board. Most are covered by a rubber coating to stop them from rolling around the boat and also to protect against accidental damage.

Lens Coatings

An absolute must on binoculars used for boating as the glare from the water can be blinding. There are many types of lens coatings available, but look for fully multi-coated lenses for the best quality coating. This will cut down the glare and improve brightness, contrast and light transmission. 

ED Glass

This is found on high quality optical equipment, ED is the abbreviated term for Extra-Low Dispersion glass. This is all to do with the way prisms work. White light enters the prism and a rainbow of colours leaves the other side. The colours are brighter when there is low dispersion plus the image remains clearer.

What Type Of Binoculars Are Best For Boating?

Almost all boating binoculars are Porro prism binoculars; this is because the shape of Porro prism binoculars lends itself well to a wider field of view that is necessary for marine binoculars. With that said, some people prefer roof prism binoculars because they are on the whole lighter than Porro prisms and often easier to hold especially if they have longer lens tubes. Roof prisms are certainly more robust than Porros but they can be more expensive too.


Many of the better brands of marine binoculars have a limited lifetime warranty. Which means as long as you remain the owner, and they are not deliberately mistreated they have a lifetime warranty.

How Heavy Are Marine Binoculars?

The weight of marine binoculars varies depending on the brand and the amount of special features they contain. The regular marine binoculars, without any special features weigh in at somewhere in the region of 600 to 700 grams (21 to 24 ounces). With the feature filled binoculars weighing in at around 1kg (2.2lb).

Marine Specific Binocular Features

Many modern marine binoculars come with added features, which of course add to their price. Some are handy but not always necessary, you’ll need to consider their usability for yourself. They include;


These vary from brand to brand, with some brands having digital display compasses that remain illuminated for convenience. While others have a superimposed image of the compass just below the image you’re viewing through the lens. This can be useful for working out the direction a distant vessel is travelling in. 


The rangefinder works using an integrated infrared laser system which estimates the distance of other boats, objects or potential obstacles. The distance is displayed directly through the eyepiece in feet or metres.  

Central Focussing Knob Or Individual Eyepiece Focussing?

Marine binoculars typically have individual eyepiece focussing as opposed to central focussing. This is just like having a diopter for each eye. It saves having to refocus every time you use your binoculars. These individual eyepiece focussing systems tend to focus at a distance of 25 yards out and beyond.

The main reason for using this type of focussing system on marine binoculars is it’s far easier to fully waterproof without a central focussing system.

Glasses wearers will find this type of focussing useful as they will not need to wear their prescription glasses once they’ve set the diopters up. 

Image Stabilisers

Direct from the camcorder industry, image stabilisers have been incorporated into some marine binoculars to compensate for the motion of the waves. The downside is the need to recharge or replace the batteries and the extra weight the batteries add to the overall weight of the binoculars.

5 Important Points To Remember When Buying Marine Binoculars

  1. Buy Specific Marine Binoculars
  2. No Higher Magnification Than 7x (unless choosing a pair with image stabilisers)
  3. As High An Objective Lens As Possible (we recommend 50mm)
  4. Fully Multi-Coated Lenses
  5. Choose Extra-Low Dispersion Glass (If possible)

Frequently Asked Questions

What magnification is best for marine binoculars?

The best magnification for marine binoculars is 7x this is the highest magnification without showing a shaky image.

What binoculars do the Marines use?

The Marines use binoculars with a magnification of 7x and an objective lens size of 50mm (7×50).

What are 7×50 binoculars good for?

7×50 binoculars are the best size binoculars for using on a boat.

Can you use marine binoculars on land?

It is possible to use marine binoculars on land but they will not be of any use under about 25 yards. For short range viewing a regular pair of binoculars will be more suitable.