Guillermo Eirin, I would start by disassembling the phone and cleaning it. Use this as a general guide. You can find a teardown for your phone right here. There is also a take apart guide on here. . Hope this helps, good luck.
Shake and wipe water off , open phone and wipe parts (try with a non static cloth ) put phone in a bowl of rice for a couple of minutes(30) that will take out extra water if next day it does not come on get a new battery and see if problem continue if it does get a new phone .