This buoy uses an elastic that's about 6 feet long when not stretched, and stretches to 32 feet. The tether is designed to give way between 6-10 lbs of force, which is more than the force required to sink the float, and less than the force required to trip an anchor. In normal conditions, the tether will remain attached to the anchor, but with force from a prop it would sacrificially give way leaving an anchor intact. There is no spring; all metal components are stainless.

I'm not sure I have a need, but it seems like a nifty idea. I don't buoy my anchor in crowded harbors because I'm afraid it would get tripped by a passing boat. This solves that problem.

The few times I did buoy it, it was to facilitate retrieval when I suspected the bottom has debris that might foul my anchor. This is not a solution for that situation.