Recovering data from a phone that had water requires professional skills and besides, it's a very meticulous job because you will have to open the device to make sure that everything still works and the components need to be dried out.
My advice is to take the phone to a repair service shop to see if the circuits and chips are in 100 % integrity or data recovery won't be possible. Moreover, if you have an Apple Shop nearby, take a visit and ask them to look at the phone.
The first step is to make sure the phone still boost and turns on, then you can focus on recovery.