Okay kiddo, have you ever gone swimming in a big pool or the ocean and it gets really, really dark as you swim deep? A dive light is like a flashlight that divers use to see better when they go deep underwater where it's really dark.
Some dive lights are small and can fit in your pocket, while others are bigger. They have a special waterproof covering so they don't get ruined when wet.
Do you know what a battery is? A dive light also needs a battery to make it work. The battery is usually rechargeable and can last for a few hours.
Divers need a dive light to see where they are going and to look at cool underwater creatures and other things that they wouldn't be able to see without the light. It helps them be safe and have fun exploring under the sea!