try doing a google satelite image search on the area (google local) You can see a good amount of what's underwater. Rocks, sandbars, eelgrass beds.... everything but the fish. The hybrid mode is pretty cool too, it overlays street names on top of the satellite image.
I've wasted many, many hours going through these things! It's a good tool.
here's a link to a map of nobska point....Check it out
http://www.google.com/lochp?hl=en&ta...lmouth%2C%20ma