Texas, thanks for the reply.
This is my first attempt at a substantial pond and I really don't have experience in this area. I think some sort of floating dock would work, but you have to take them out of the water each fall before things ice up. Liquidsquid described how thick ice tore the wooden posts off their concrete footers when the ice thawed along the shore and then the ice around the dock moved, so lateral motion is certainly a concern. Also, any structure in the water is at risk if the water level changes when the pond has ice. My approach is to set substantial posts, in concrete, and keep the cross members out of harms way. I don't know what "out of harms way" implies and I want the dock as low as possible. Just no experience.
Thanks again.