If it was real mushy sand, a lot of water mixed in with the sand, example (where my feet would sink quickly) the ring did the same. It didn't move very far from where I dropped it. Almost straight down and I'd imagine it would sink until it hit something hard, example the layer of crushed shells etc. Never stood for long periods of time to see where or how much of the fishing line disappeared. Now on the other hand, if the sand was hard packed it's movement depended on the frequency and speed of the incoming wave action. It was very common for the ring to stay within a 3 foot square for a long period of time. Well as long as I stood there. Now here is the kicker to the issue, if the waves were heavy laden with sand I would lose sight of the ring almost immediately regardless of hard or mushy sand. Hopes this helps. I don't know everything about the subject but it is very interesting to say the least.