Creating a Freshwater Splashdown for Spacecraft
Using proven technology, turning the great garbage patch into a resource. Sequester the debris in artificial reefs, creating a fresh body of water.

Vast areas of the ocean collect plastic debris:
http://www.greatgarbagepatch.org/
http://www.algalita.org/

Spaceships need to splash down into freshwater. Saltwater is too corrosive; water landing may be safer than landing on land.

Small electrical currents precipitate calcium from seawater cost-effectively creating artificial reefs.
http://www.arcoscielos.com/

http://beyondearth.org/: a book sponsored by the Aerospace Technology Working Group; also a project to create "1,000 Earth-based Space Stations" to inspire and educate, and to catalyze the political and financial will to commercialize and settle space.