They do pump water out and back into the locks from neighboring storage. There is a limit to the minimum amount of water that you can use, though, since the po

They do pump water out and back into the locks from neighboring storage. There is a limit to the minimum amount of water that you can use, though, since the potential energy to raise the ship comes from the loss of water. https://www.youtube.com/watch?v=SBvclVcesEE&t=338s https://www.youtube.com/watch?v=SBvclVcesEE&t=338s