Apple iPhone data recovery Extreme Conditions.
Apple pretty much offers only one option if you ask for help which is "reset your phone." This video goes into deeper detail about one company and there are others out there that will give it a try.
The best news is that they only charge 300USD if they are successful. And the estimate is that about 95% of the phones can get the data recovered. Of course this declines the longer a person waits after the dunk or damage.
Apple isn't pleased about third party support or repair so they ban folk from the Apple forums that talk about this work. Here's the video again.