We used this with the kiddos at the beach and it worked flawlessly! We kept it in backpacks that got soaked and I can confirm it is waterproof after an extended period of time. This detected metals at about 7", a little shy of the 8.5" mentioned. We ended up purchasing a second for the kids to share and are extremely pleased with these! We plan on buying a metal detector one day and then using this with it to pin point the goodies, but in the mean time, the kids are content using this.