Why would you need to remove it from the water every winter?
If you search on here, you will find some threads about building a floating dock or floating pier. I have a pretty detailed one.
Have you looked at this place?
http://www.dockbuilders.com/ You don't even have to anchor it to the bottom if you have a wide "base" that is on shore. Bruce Condello has a really nice one that Nate, Justin, etc., (Herman Brothers Pond Management) built.