Exactly! I'm working on some stuff now to exploit this very effect, the small time difference in the bands can be used to find velocities of moving objects.
That's not what I'm doing but it seems possible you could watch refraction patterns and tell that there are submerged objects, but you'd need to know the water depth without that object there, as there'd be no great way to tell if the object is a submarine or a pile of sand. Also, most of these satellites pass over fairly rarely so wouldn't be super useful for tracking things that move. I'm mostly interested in finding the piles of sand :)
