We had the same problem. Our pond, after many years, was filled with silt and weed growth. The muck and loss of depth made it unswimmable. The pond life was healthy so we wanted to preserve it as much as possible so our approach was to draw down the water, get rid of most of the muck (except in the middle), increase the depth, and add a dock. I documented this project in a photoshow, which you can see at the following link. We're very happy with the results. (NOTE: For best viewing, click on the full-screen button when the photoshow starts loading.)
Pond Renovation Project
http://www.photoshow.com/watch/PK8SR5KdSam Robbins
