Wet iPhone
I went surfing with my iPhone and it died.How can I access messages I had on the phone?
Question marked as
DO NOT throw away your phone, as mdp1101 suggested.
While the Apple One Year Limited Warranty does not cover water damage, nor does Apple repair liquid damaged devices, you can get a replacement, either out-of-warranty, or if you purchased either of the AppleCare+ products, the damaged phone can count as one of your two covered incidents. See the following for costs, as you don't mention what model phone you have.
Other iPhone repair costs - Apple Support
Just for future reference:
Water and other liquid damage to iPhone or iPod isn't covered by warranty - Apple Support
About splash, water, and dust resistance of iPhone 7 and later - Apple Support
As for your messages, you can restore them to your replacement phone via an iTunes or iCloud backup.