Go to
http://www.stagecoach-wireless.com/Cameras/SCSH/Pos3.htm
The picture shows a sailboat mast with Steamer Lane in the distance. I happened to look at it early this morning and saw that the top of the mast was below the horizon - I forget by how much - and it was a -1 tide. Looked at it again about 8 hours later and the masthead is somewhat above the horizon and the tide is about 3.6. The boat has been there for months. It’ll be a good measuring tool if they don’t leave. You could draw some tickmarks on your screen for greater accuracy.