If they are swimming up to your property and then walking onto the shore to get onto your dock, there is an easy solution. Pound in some stakes close to the shore and leave them sticking up about 18". Tie wire or cord to the stakes a little over a foot off of the ground connecting the stakes. You are making a "goose fence". For safety, tie some bright ribbons to the wire/cord was a trip alert.
The geese won't hop over or duck under.