Shallow water wrecks are easy to see from space with a big enough block of Nikon's finest zoom glass, and the best of Kodak's space rated films, simply by looking for the telltale ship sized reefs in the clear water at noon. Less vibration than in an aircraft, and a slower motion across the area. however, a local magnemometer survey across these locations is needed to find the telltale signature of iron cannons lying on the sea floor, and this really needs to be done from under the surface, and with a wooden ship towing the sled. At least that satellite imagery can reduce the area you need to scan from " a whole lot of blue water" to "just these bits of water with a shadow on the sand", which saves a lot of time.