Water seal
Unfortunately, those water seals don't just change if exposed to a sudden submersion. They are also prone to change, over a reasonable period of time, if they are just used in a humid area, a damp country or by someone with slightly sweaty hands. In fact, pretty much any use of a mobile phone that could be considered reasonable and normal will trigger these things over a period of a couple of years. Which gives HTC a great "get out of jail free" card when it comes to honouring warranties on devices that have genuinely developed a fault entirely unrelated to "water boarding" or any other form of liquid based communications device torture.