You are allow to bring your phone under your own risk, you must know that rafting involves a lot of friction between your body and the raft, and safety gear, so whatever is attached to you body may get stock with a rope, paddle or river obstacles risking your safety and running the risk of losing your personal objects. The bottom of the rivers where we go for rafting have a big collection of treasures like camaras, go pros, sunglasses, jewelry, phones and watches. Both of your hands will be busy using the paddle so there are not many chances of using your hands for taking photos or videos. In case of bringing your phone in a dry bag, the best way to tie it up is under your PDF(personal flotation device) with an extra string attached to the straps, however full configuration and attachment must be done directly by the customers, guides are not allowed to attach cameras due to safety policies to protect them in case of losing stuff. Hard boxes or cases are not recommended since it may cause bumps and injuries to passengers.