FAQ about dive lights and underwater cameras
They are very similar, however the BUTTON version enables multi-function power on (that is not available in the TWIST) offering a HIGH and LOW lumen output and a safety STROBE setting. The area around the button feature is illuminated and will give an approximate battery life remaining notification with color changes.
Most experienced divers prefer the simplicity and reliability of twist-on style lights, but divers can become confused about the twist direction and flood their light. The button-on style light is less likely to flood as a result of user error, but the mechanical nature of the button switch itself is an additional point of failure not present in the twist-on design.
The choice between twist-on or button-on styles is mostly a matter of personal preference, but we do have recommendations for a few specific applications. Button-on style lights are easier activate when used with hand mounts or helmet mounts. If you are mounting the light, we recommend the BUTTON style. If the light is being carried as a handheld backup to a primary, we recommend the TWIST on style. Better yet, if taking two backups for technical diving we suggest one of each style.
There isn't a manual, however there is not much to know. To load batteries in the DGX lights, unscrew the head from the body until the two pieces separate and then insert the battery or batteries in to the body, negative end first such that the positive end will be pointing toward the light head. Hold the head and screw the body clockwise back together all the way until it stops. Briefly push and release the button on the models with a switch to turn the light on or off. To turn off those models without a switch, twist the body counterclockwise until the light goes off then continue to twist the body one half revolution. Once assembled, the twist-on model lights should require a maximum of about one full revolution to turn on or turn off. Do not store any handheld light for extended periods with batteries remaining inside the device because over time batteries can self-discharge and then leak acid.
That's all there is to it, some models also include a little bag of spare O-rings should you need them. There is nothing special about the lubricant, any generic silicone O-ring lube used with underwater equipment will work. If the O-rings ever start looking dry, leave them in place but smear a very small amount of lubricant on the part of the O-ring surface you can see. You might also benefit from reading How to Use a New Twist-On Handheld Dive Light.
Most often the reason is a dead battery plus an error by the diver that causes their handheld "twist on/off" flashlight to flood. The diver twists the light in one direction to activate and nothing happens, so the diver twists the light in the other direction attempting to activate and nothing happens. Then the diver keeps twisting in wrong direction, breaks the O-ring seal and it floods. Other less common reasons are failure to maintain correct amount of lubrication on the sealing O-ring(s); dirt, hair, or salt introduced on the O-ring(s) or sealing surfaces when loading batteries; over-tightening the light head and body together; and finally leaving batteries (especially alkaline chemistry batteries) stored in the light over a long period of time.