When I got my iPod I faced the same issue. I purchased the drink holder mount (see photo) which I thought was a good idea, UNTIL I realised having the iPod exposed to a bow wash etc was too risky.
I then switched to an Otter Box (see photo) purchased some long AV cables and now have my iPod floating around my boat. Water's not a problem now, the only risk is if we drop the iPod overboard.
Hope this info helps.....