So, a sail? It might not be traditional and look like a giant parachute, but I'm pretty sure we've been using wind to go across the oceans for quite some time.

The improvement here is that it can go as high as 300m (1000ft) and winds are much stronger there. And once you're done or approaching the harbor you can furl it in and never think about it again. Sails... not so much. Especially on ships of this size!

Even an improved sail is still a sail, though.

I seem to remember this in waterworld :). Yep sailboat.

That was my first thought as well.