Peter Diamandis talks about the ocean exploration prizes under consideration.
Whether robotic or human-piloted craft result from the prize(s), these strike me as having as much or possibly even more potential than the space prizes.
Certainly there's a great deal of intrinsic economic and scientific value in exploring the Earth's oceans. In addition, some of the skills we would learn as we explore them would be highly applicable to space (and I don't mean just oceans under icy moons), whether it's advances in vehicle subsystems, instruments, extremophile science, and so on. Many of the details would be different, but just as scientific study of the other planets helps us understand the Earth, and vice versa, the NewSpace and NewSea industries should be able to complement each other.