OK so I am sure that I am not the only sailor that has dropped a cell phone in the water from my pocket whilst bending over to tie the boat to the dock.
Assuming that you can get the phone back, I managed it with a kids fishing net attached to a boat hook as the water was not too deep, what do you do next or is a waste of time?
If the cell phone or other electronic device was dropped in salt water you need to rinse it thoroughly under the faucet, I know this seems like the wrong thing to do but trust me you need to get rid of the salt crystals. Remove the battery if you can as this makes cleaning out the inside easier. Shake off as much of the excess water as you can then pat dry with paper towels. Finally bury the phone or other electronic device in a clean dry bowl of rice and leave over night. The rice will attract and absorb most if not all of the remaining moisture left in the device. With luck the phone or other electronic device will have survived and lived to ring another day.
Even if you manage to dry out the equipment it would be wise to get it to an approved service center asap so they can take it apart and check the inner workings.