RE: Loading troops and equipment back onto waterborne transport vessels
As far as I know, you can embark again on a vessel as long as the ground unit and the vessel are in the same hex. I have done it where there is a beach or shallow water hex.
If there is no such hexes or your transport is not amphibious to move onto a land hex, then you are out of luck.
Fast is fine, but accuracy is everything.
- Wyatt Earp