This is an essential guide to help you choose a flashlight best suited for sailing, or any water-based marine activity for that matter.
When buying any kind of light source for sailing, especially when it comes to directed compact handheld lights, such as flashlights, you will want to pay attention to 2 very important ratings of the product: water-resistance or water-proof rating, and the lumens rating.
There are several considerations for what the water-proof rating should be and how many lumens you should consider when buying a portable handheld light source or flashlight.
Water-resistance or Water-proof Rating
The best rating system we currently have available is the International Protection (IP) Code System (International Protection Marking). The water-proof rating that you should be looking for is IPX8, as this rating means that the flashlight can be submerged in water below 1 meter (metre) in depth. IPX7 is good as well, but it is rated to only 1 meter (metre) of depth in water. To simplify the understanding of water-proof ratings and learn more about this topic, we have written extensively about it in a guide to understand waterproof ratings.
A lumen is essentially a unit of luminous flux, which is just a fancy technical term for light intensity for a given area. The more lumens your flashlight emits the more powerful the flashlight is and the more capacity it has to illuminate objects from a greater distance. Determining how many lumens you should consider when buying any type of portable light source depends on what you plan to use that light for. You will probably need several different types of flashlights for different purposes.
There are several factors you should consider when determining how many lumens your flashlight should have: distance, size, and safety.
If you only need a flashlight for everyday activities, where you only need to light up objects in your near proximity (within a few meters) then you will only need a flashlight in the (low) hundreds of lumens. With a generic everyday-carry (EDC) flashlight or headlamp, that you may carry on yourself, you can get away with the flashlight or headlamp having, at most, 200 lumens.
During critical operations at night time where you want to minimally light up your surroundings but do not want to affect your eyes ability to see in the dark distance then you will want to get a light that supports a red light mode. Colors of light in the red side of the light spectrum help to preserve your natural night vision. This is why most car dashboards light up with orange or red LED back-lights, so that you are able to read your car's instrumentation without having that light blinding your vision when you look out at the road through the windshield.
If your flashlight does not support a red light mode then you can buy a red lens cap or filter adapter -- make sure to buy a lens cap or filter adapter that is compatible with your flashlight.
If you need to light up objects farther away, from 10 meters (metres) to 200 meters (metres), then you will want a significantly more powerful flashlight with lumens in the 200 to 1000 lumens range. These types of handheld flashlights would be useful during mooring, docking, and anchoring.
It is also important to note that the concentration of lumens in a given flashlight also has size limitations. Naturally, a larger flashlight will have a larger lumen capability, but you will be surprised how small of a flashlight can that can output 1000 lumens, which is quite a considerable amount of light.
Generally, you are using a flashlight to light up dark areas, but safety is not limited to just illuminating your surroundings. One consideration, that many people do not think about often with a light source, is personal safety from criminals (pirates) that you may encounter at sea.
Some people consider having machetes, knives, guns, clubs, spears on-board as a form of "active" safety against people who may board your vessel. Additional considerations should be looked at as well, such as "passive" methods of protection from criminals trying to board your boat. One example of a passive method of protection is to have a very powerful (4000+ lumen) handheld flashlight on-board that you shine directly on the person(s) that you do not want to board, aiming the light directly on their face. Doing this would immediately make the person react by trying to protect their eyes, as such a high-intensity light would temporarily blind them, and temporarily immobilize them, potentially slowing them down, allowing you to get away and helping to, potentially, prevent them to board your vessel entirely.