Interesting thoughts.
The possibility of launching a rocket from the sea/lake bed has been taking to the point of trials but I don't see evidence of alternatives being discussed i.e. building a skyscraper sized water container under ground and high above ground. This would offer a lot of control. No salt. No current.
Ignition would happen on the external portion of the container which makes incidents easier to deal with.
I can imagine an additional air filled container under a rocket to add to its initial lift then providing a surface for rockets to propel against.
The thought of a rocket or the latest space planes reaching good speed before spending any fuel is too intriguing.
