Hey, 3 to 4 hours is really a lone time for an iPhone drop into water. I think you first need to get it out of water. Then, turn off your iPhone and put it into a bag of rice. If you are near to an Apple Store, you can directly bring your iPhone to Apple Store for help. If you do not want to go, you need to wait for 24 hours or more to let your iPhone dry and then you need to turn on it. If it can turn on, you are lucky. if not, you need to go to Apple Store for help. For iPhone users, data is always the most important thing when you lost or damage your iPhone. So if you have iTunes or iCloud backup files, you can restore your new iPhone with iTunes. If you do not have backup files or the backup files is really old, I don't think you can get back your iPhone's data. If you can turn on your iPhone, you can try iPhone Data Recovery. It can recover data for your iPhone. I just say if you can turn on your iPhone and it does not guarantee 100% recovery.
Hey, Actually you have 3 ways to recover your lost sms from your iphone 6. iTunes backup file, iCloud backup file and recover from your iOS device directly. For first two ways, you need to have the backup file from iTunes or iCloud. If you do not have the backup file, the only way to recover lost text messages from iPhone is to recover from the device. iPhone Data recovery software may help you to do that. All the software you can find online claim that they can recover your delete/lost sms from your iPhone. However, not all of them work like they said on their website. I have tried some of the recovery software online and find this guide, I think it is the best one for now. http://www.iphone-datarecovery.com/recover-iphone-data/recover-deleted-text-messages-from-iphone.html