Thanks for the comment, Bruce.
With the red boat I suspect it has become bow heavy which is making the boat tip downwards as it grounds. Probably a build up of rain water which runs towards the bow as the boat grounds. But there is a potential risk with this type of mooring. If the boat repeatedly turns in the same direction the mooring chain can become twisted and shortened. The usual practice is to incorporate a swivel into the chain to overcome this potential problem. I normally used two swivels, one below the buoy and one between the buoy and boat. I have know boats to sink as a direct result of a twisted mooring chain which held the boat down as the tide rose.
That area is a river estuary and the location is well up the estuary so the boats tend to be less well cared for than those which moor closer to the harbour entrance.