It's never a good thing to have your phone end up in water (even if it's waterproof), and the likeliness of permanent damage increases if it's salt water or chlorinated water. So if you drop your phone in the sea this summer, act as fast as possible. Take it out, turn it off, take out the battery and wash it with fresh water or, even better, 96% alcohol in order to prevent oxidation.
Don't use a hairdryer and don't blow on it, because that will only spread the moisture. Instead, use silicone balls.
Leave it to dry out for a minimum of two days using silicone balls or rice and then try to use the phone, checking the touch screen and the speakers, in order to see whether it needs to be taken to a repair service after all.