My two cents: I believe space will continue to be explored, eventually resulting in space colonies. I don't think it'll proliferate in the sea. It's so much easier and cheaper to simply build taller buildings than to keep the water out below sea level.
Looking at the space stuff from a distance, only 12 men have ever walked on the moon, and the last one did so in 1972, about 9 years before Epcot opened. Only 21 people have ever left Earth orbit. More recently, the International Space Station was hugely hugely hugely expensive, yet it has yielded virtually zero in hard scientific advances to help makind. Every year, Discover Magazine publishes a list of the 100 biggest scientific advances of the year, and I do not believe that any of them over the past half dozen years or so have had anything to do with the ISS. This huge budget-busting project has yielded essentially nothing beneficial to mankind.
By contrast, the unmanned projects post-Apollo have had some huge successes, from the Hubble, the interplanetary missions, the satellites, GPS, weather forecasting, and even back to the Voyager missions.
Eventually I believe people will return to the moon and beyond. It'll be expensive, but I think it'll happen. Just remember, the moon missions would probably never have happened if not for the cold war. Watch the brilliant first episode from HBOs From the Earth to the Moon. They fear a "red moon". In large part, the space race was about winning allies with our advanced technology. After all, the Soviets beat us into space with Sputnik and Yuri Gragarin, so the only thing left was to beat them to the moon. We did, and perhaps averted WWIII in some twisted way. Of course, the true scientific discoveries and betterment of mankind resulted from the tech arising from the race itself, not from any amazing discoveries from what they found on the moon itself.