Millom Coastguard Rescue Team posted this on FB and it has been shared by many.
Could rock up in other places too.
I hadn't heard of it before, they look just like parsnips.
Thank you @Jacqui-S , I will inform my son, he spends a lot of weekends with his mates on the Welsh coast. Different part of the coast I know, but who can tell where these might appear.