Stupid question, but how you switch map types?

I was unable to use this spell to create a land bridge that I could actually walk across.  It doesn't seem to work well on shorelines at all.  Looks like non-harbor shoreline squares are impassable ("cliff" squares, I guess), even if you raise land out of the sea on the other side of it.

yes it has been my experience that to make a land bridge, you need to raise up the square you'd like to walk on and every square on either side all the way across. I'd recommend having a team of casters for this

creating usable shoreline is similar except you want to raise a water tile adjacent to a cliff, then raise the tiles along the cliff to either side of the first tile. also, you need to have your city close enough to the shore to build on it, remember harbors are improvements, so you need available tilespace near them to build there.