You can use one end of a larger pond. RetrieversONLINE has a free downloadable article on swimby with diagrams on how to use one end of a pond.
There was a recent video of a trainer using a place board and one corner of a large pond to do swimby. I can't remember the name of the person doing the video. I will do a search and see if I can find it.
Edit: Here is the youtube video by Pat Nolan.
Dave-you still in Lemoore? I lived there as a kid.