Another way to look at the problem is to go to a chart http://marine.geogarage.com/
and just noodle around and see what the depths are where you have an interest.
Back in the day 1985 when I was in that neighborhood I had an O'day 22 with a fixed keel 23". Didn't have a depth sounder, didn't need it, used the knees of water foul and a binoculars for depth. Had to know your birds though!