Underwater lights : Lumens vs Fixture lumens
Many underwater lights manufacturers advertise their light capacity in Lumens. This will eventually determine the depth of penetration into the water of your light. It is useful to know that this light intensity is actually expressed in 2 ways, in Lumens or in Fixture Lumens.
Lumens means the intensity of the light emitted by the LED itself while NOT installed inside the fixture (the light housing) Fixture Lumens means the intensity of the light emitted while the LED is installed already within the fixture. Typically the Fixture Lumens expressed will be about half of the Lumens. Obviously the important factor is the Fixture Lumens as this is what you will end up seeing on your boat. Be sure to compare apples to apples and Lumens to Lumens and Fixture Lumens to Fixture Lumens.
If a manufacturer publishes only Lumens then ask more questions to obtain the correct data for Fixture Lumens which you can then properly compare to other manufacturers.
Do proper market research to get the best performing lights for your boats and distinguish properly between Lumens and Fixture Lumens.