How big of an explosion in exploration do you mean? I'm sure there will be several occasions when a new system will allow a significant growth in exploration. I'm thinking about the critical change where private companies and even individuals will be able to conduct activities in space as easily as they now conduct activities on other continents, without any governmental support.
I'm no big fan of NASA myself, I was just using their stated goals as an example. I'd be delighted to see other approaches worked out by private concerns. But even so I don't see that a much more accelerated time line could be achieved.
Laser Lightcraft are only intended to lift one Kg or so to orbit. For larger masses a Microwave Lightcraft can, theoretically, be used. The energy equations for such a device do work, but the technology still has a long way to go. There is also the possibility of the Space Elevator. Again the energy equations are sound, but the technology is not there yet. A long shot maybe, but who knows. There are no doubt other possibilities that no one has thought of yet.
My point is that as long as we stick to the idea of carrying your fuel ( the rocket paradigm) the costs will never drop as much as they need to for space travel to be worth the expense.
I'm not sure I entirely understand your water scheme, but if it would result in greater investments in developing conventional and unconventional launch technologies then I'm all for it.