I used these radios with my soon to be 10-year-old son:
http://www.motorolasolutions.com/en_us/ ... os_generalHowever, they only float if they have the manufacturer's rechargeable battery pack in them. If you put regular AA batteries in them, they will sink.
I hate the rechargeable batteries. So I use regular AA batteries and have attached a float to the radios.
If you use a headset with them; they will not be waterproof. The receptacle for the headset must be covered in order for it to stay waterproof.
I tested them by dunking them in a bucket of water. They are, indeed, waterproof. However, you must blow the water out of the holes where the speaker is. Unless you do that, you will not be able to hear any of the transmissions from the other radio.
IMHO they work great for the price. Getting a 10-year-old boy to use them properly is another story.