There have been more than a few questions covering Alcubiere warp drives, many about what happens with one at FTL and a few about using them at sub-light speeds.
I'm curious about what happens at more pedestrian speeds (tens to hundreds of kilometer per hour as opposed to percent light speed)
If someone fired up their warp drive underwater what would happen? More specifically, what happens to the water outside and at the boundary of the warp bubble (I'm guessing that the water inside the bubble gets moved around much the same as the ship)
Please ignore the practicality and the general absurdity of creating what amounts to a warp-powered submarine.