We were there on a ball at the southern end of Manchioneel Bay a few weeks back, and a 40ft mono dragged their anchor about half the length of the bay while the crew was snorkeling at Cistern Point... they raced back to their boat when they realized what was going on, but she moved pretty fast! Fortunately the drifting yacht didn't collide with anyone else - but the anchor must have made a mess of the grass on the sea bed!