This underwater light is a unique one. This was easy to use because the strap is Velcro so all you have to do is just pull it around your wrist. This fit mine just fine. The nice thing is that my daughter was able to fit it also. She wanted to use it in the pool. You can use the large battery 18650 that is rechargeable or three triple A batteries that can fit in the cylinder converter. This does not come with batteries but you can easily get them online. The bottom part where the battery goes has three rubber gaskets on it for sealing it and making this water proof. You can get one here https://www.amazon.com/BlueFire®-Waterproof-Flashlight-Underwater-Submarine/dp/B01FVHU9CA This comes with a wrist strap that you can use to have it hang. This is a bright neon color so it can be easy to find if you lose this. This is light weight and small enough to pack in a purse or bag. The light is very bright so you can get good coverage. Overall, I would recommend this because of how good it has worked for us. I received this product for free in exchange for my honest and unbiased review.