It's a tutorial, not a filter. Forget where I found it. sorry.
You make a special kind of .PSD file and you select the reflection (water) then Filter->Distort->Displace
A menu pops up and you select a percentage (10's good) then it asks for the special .PSD file. You pick it then it does it's thing.
I uploaded my special .PSD (forget how to make it, you should be able to use mine)
<link>It's a little less than 5mb