If your only getting three led flashes then the operating system is corrupted.
If you updated the system using the wrong software or loaded an app that caused the problem then it can be fixed. If the phone has other issues from water damage or being dropped then it may not be fixable.
Try reading this link to restore the software. Follow all the directions and do not rush. KB11320-How to perform a clean reload of the BlackBerry Device Software using BlackBerry Desktop Software for Windows