Construction design
A dive light should be designed with solid and compact size, easy operated, good waterproof, especially at the switch part. So you need a real test underwater( as deep as you can). But before you do that, you can also tell if the construction was designed well by some details.
1. You can twist the connection part to check if it can be connected or disassembled easily. Check if any noises are made while doing this. Check whether the threads will cut the O-ring or not.
2. Check if there is a strong feeling when you press the switch down. You need to know “oh yes the switch is pressed down already”. Tips: Wear a glove to test is better. The switch should be easily located when you wear a glove.
Optical design
The alloy aluminum reflector should be designed with professional optical analysis. Please check the light beam on the white wall, the central spot should be tight enough so that when you wave the flashlight to communicate with your buddy or divemaster, for example, a circle to say “ok”. Your buddy can see it clearly and got what you mean. Besides that, the beam should be uniform with no black spot in the center or dark circles.
Exquisite workmanship
No knife grain, no white spot, or scratching on the surface.No sharp edges especially the part of the lanyard hole, or it will easily cut the lanyard and lost your torch. Hard anodized finish, please test corrosion resistance in seawater.（Some factories just produce it with normal anodize finish, and it increases the risk of corrosion）
Material
Aircraft-grade aluminum flashlight body, gold plated spring with enough strength and good conduction, high-efficiency PCB, 4~5mm toughened glass, high quality LED from Cree/luminus or any other famous top quality LED brand. Durable O-ring that would not be worn out easily. These are the top materials for a top-quality dive light.
Assemble
No dirt or foreign matter on the light cup or LED. So a dust-free planet is necessary to make sure of that.
No dirt or foreign matter on the light cup or LED. So a dust-free planet is necessary to make sure of that.