That looks like some solid clay! I hope those underwater structure features stay that way for a long time.
It is great clay! When it dries out it is as hard as concrete... It will also stand vertical for 10-15' no problem...
I know some of the areas will silt in through time, but with limited runoff coming from grassy areas, the silt load on the pond should be minimal. There should also be limited shore erosion since two sides of the pond will be lined with rip rap.
Any guess under those circumstances how long some of these shelves with last? 10-15 years?
