interesting, unfortunately, like most others, i know nothing about it. But it is really interesting!
can you link online sources to this all, the whole subject? Maybe some of us can somehow help after we did read up on it. Also to the others, related links explaining what it is about? i could go into questions like.... is the water underneath steady or free to move, how far above the water level is the ground for the snake, etc, many questions. But sources, and then reading up, and then suggestions/questions is probarbly the way to go.
EDIT: so much i do know: big stones are the problem, since you cannot easily turn small stones into big stones. Small stones are no problem, just combine the following: hammer, stone, outdoor. Dont discard a stone because it is too large, show some manlyhoodSounds like quite a soft stone anyway.