Did you open it up, pull the battery out, pull out and SIM and SD cards and leave it to dry for days? If not, it probably has water in it still, which can do lots of damage. You would need to do all that and leave it for a few days to make sure it is dry. Then put it all back together and see if it will work. It may need a charge then.
If that doesn't help, then the damage done by the water was worse than it could have been, due to using the phone right away.