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.

Worst case your phone is no good after, it's the motherboard

go on eBay for a cracked screen one, but ask for the IMEI and check it to see if it's blocked before you buy it and use that motherboard

use the guides oldturkey03 linked

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 .