Sorry to hear about your leaking issue - many of us share the pain of that situation. I'd get a quote for clay compaction and consider the effort draining and drying the pond then contact me for a chat - a polymer treatment could cost a fraction and wouldn't require any of the draining effort. It's worth a chat, happy to help any way I can.
Many men go fishing all of their lives without knowing that it is not fish they are after. ~ Henry David Thoreau