Graham Hall on Navigation

But at other times we did have quite a number of wrecks that sank, and we had to go out there. There was some pretty bad weather sometimes and try and locate them. Once we’d located them, we then had to survey them to see how the depth of water was over the top and we used to do this by the tried and tested method of chain sweeping.

To do this you used to hang small link chain over the side of the ship in rows from the bow to the stern so there would be lots of lengths of chain with a weight on the bottom to keep them vertical, hung over the side of the ship and the bottom of them would all be joined up with a piece of spun yarn, a piece of line and you’d then position your ship so the tide would drift you over the wreck and you’d set all these chains to exactly the same height so you knew what height the depth, the line was at the bottom and as it swept over the wreck, if there was anything sticking up it would file and you could see the chains go out and the spun yarn would break so you kept on raising it up and up and up and you’d keep on doing this until it passed clear and then that was known as the swept depth of the wreck.

That was the swept depth of the wreck so that’s, we did that. We did several … certainly down off Arne Point, off the entrance to Poole. We did one just south of the Island, the ‘Poole Fisher’.

We never really found that one, it was a difficult wreck to find.