will apple fix a wet iphone 4

No, your warranty is voided if there is evidence of water damage.

You can do an out of warranty replacement ($199 in the USA, for example)

"an iPhone that has failed due to contact with liquid may be eligible for out-of-warranty service."

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Out-of-Warranty Service

If you own an iPhone that is ineligible for warranty service but is eligible for Out-of-Warranty (OOW) Service, Apple will service your iPhone for the Out-of-Warranty Service fee listed below.

A $6.95 shipping fee will be added if you arrange service online or by calling Apple Technical Support. All fees are in U.S. dollars and are subject to local tax.

When setting up out-of-warranty service, Apple will request credit card pre-authorisation for the maximum service fee listed above. This amount will be deducted from your credit limit. The final service fee we charge will be determined during testing and may be less than the service fee listed above.

Certain damage is ineligible for out-of-warranty service, including catastrophic damage, such as the device separating into multiple pieces, and inoperability caused by unauthorized modifications. However, an iPhone that has failed due to contact with liquid may be eligible for out-of-warranty service.

Apple reserves the right to determine whether or not your iPhone is eligible for Out-of-Warranty service. iPhones that are repaired or replaced have a 90-day limited hardware warranty or assume the remainder of your standard warranty or AppleCare Protection Plan for iPhone coverage, whichever is longer. Please see Apple's Repair Terms And Conditions for further details."

http://support.apple.com/kb/index?page=servicefaq&geo=United_States&product=ipho ne