I'm looking for a floating dock too.
I love this dock but it's very pricey -- with shipping about $350. He will give a professional discout of 10% if you tell him you're with splash dogs. Maybe if several of us wanted it, we could get a better discount.
http://www.navstore.com/doggy_dock.aspx
Here's one much lless expensive.
http://www.dog.com/ItemDetail.aspx?ItemNo=101250%20002
And Cabela's, sponsor of dock dogs, has a selection of dog docks.