I have worked on ship wreck searches and treasure recovery projects. If you are looking for wreck near rocky shore or in shallow bays the problem is those wrecks are usually flat and buried so side scan sonar doesn't do you much good. If you are lucky enough to have a magnetometer and know how to use it, you can narrow down search areas and then search grids on the bottom with hand held metal detectors, but it is a slow process and a massive undertaking for one person (but it is fun as heck! ) As far as I know those rigs only pick up ferrous metals, so wood and stuff wouldn't be detected. To find wrecks from 1700's or newer, probably the best place to start is the library . . . really ancient stuff, sounds like your common sense reasoning might be a good place to start, and then a LOT of diving ...