I found several ways for when you're stuck (can't move):
- change the active character to a pixie. These guys really are smaller and can continue where the larger guys get stuck with their heads in the ceiling.
- when you get stuck with your ship: go swimming to a place where there is room all around. Then create a portal there (moon 6). Go back to ship and aboard (click wheel) and cast teleport. Then you'll teleport to the created portal complete with ship! By the way: this trick also works with a horse. (mine is between dragon spire and Brimloch Roon currently.)
Be careful not to enter dungeons or cities mounted: they eat horses there. (your horse will be gone when you leave again.)

Actually, your horse will just be left outside the gate. You start off further away than where you clicked to go in, so if you turn around and look behind you, you'll soon see it again.