A close family member is the Southampton Harbour Master. Though Osbourne Bay is out of his "area" he was ware of them being laid. He is speaking to QHM to fine the reason for them. I have checked the notice to mariners and there is nothing - Queen's Harbour Master - Portsmouth - Local Notices To Mariners
I am sure he will update me when he hears anymore.
Though I feel it’s good to keep our coastlines looking good and healthy, it is somewhat of a shame that this has happened. We are taking our boat over there tonight for a BBQ (on the boat) so will have a look for myself.