The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.
I could put matting down, but it's fairly expensive stuff for the area that would need to be covered, and gets washed around in winter storms. That's why I suspend a mat beneath the boat. It's always just in the right place when the boat rests on the bottom
Oh, and the strip of weed to the right of the boats is growing on rocks which form a fish trap. Tide comes in, fish come in over the top, tide goes out, fish get trapped. Ready for the picking.