Sorry, but since water damage is not covered by the warranty, you'll have to pay the reduced price for a new iPhone, called the Out-of-Warranty-Service fee.
Out-of-warranty repair service
If your repair isn’t covered by Apple’s One Year Limited Warranty, AppleCare+, or AppleCare Protection Plan, your iPhone might be eligible for out-of-warranty service. For example, liquid damage isn’t covered by warranty but might be eligible for out-of-warranty service. Some damage isn’t eligible at all, for example if your device has been broken into multiple pieces. See Apple’s Repair Terms and Conditions for complete details.
Read Apple’s Repair Terms and Conditions
Model |
Out-of-warranty service fee |
Battery service* |
iPhone 6 Plus |
$329 |
$79 *available only if battery fails Apple’s diagnostic test |
iPhone 6 |
$299 |
iPhone 5s, iPhone 5c, iPhone 5 |
$269 |
iPhone 4s |
$199 |
iPhone 4, iPhone 3GS, iPhone 3G, Original iPhone |
$149 |
Plus a $6.95 shipping fee, if required. Fees are in USD and exclude local tax. Pricing is for service through Apple. The final service fee we charge will be determined during testing and may be less than the service fee listed above. Pricing and terms vary for service through an Apple Authorized Service Provider.
copied from Service Answer Center - iPhone
You can contact Apple Support to handle that or visit an Authorized Apple Service Provider or Apple Store next to your place:
Find an Apple Authorized Service Provider
iPhone - Contact Support - Apple Support