The descriptions of the shipwrecks pictured on that site all seem to be in water shallower than 15 feet. To make their point about how clear the water is, it might have been useful to show some shipwrecks that are deeper than a swimming pool.
It really boggles my mind that a 130-foot ship can "sink" in only 6-12 feet of water. (I know that 130' is the length, not the depth, but...) A tall guy could stand on the keel of that wreck and still keep his head above the surface on a calm day.
On the other hand, shallow water might be even more dangerous because every wave smashes your ship against the bottom.
