Hi Sharkitty,
I looked up Fish Hearing on google and got quite a few results. But the results are really technical and goes into the anatomy of fish. To give you an example, here's a link to a site.
http://www.ariamarine.com/Fish_%20he...sh_hearing.htm
As far as I know, fish are quite sensitive to vibrations, and can feel them in the water. I don't think fish have very good hearing though, and rely more on touch, and sight. Maybe another member would be a better person to tell you about this because I don't know to much about the subject. Hope I helped though!
Ali