I saw this on the news today, and discussed it with my dad... I REALLY don't see how a cloak could ever work on Earth... think about it... ok... we cloak a plane. Fine. But physically, as an object, the plane is still there... thus, any light hitting the plane, would cast a shadow on the ground, giving away the fact that there IS something there. The same with a person... you can cloak the item itself... but the fact of their physical presence remains, and thus, the uncloakable shadow.
Same principle for a boat-cloak... it would be given away by both visible depressions in the water, not to mention a foamy wake that appears to be coming from nowhere.
