And this is where the fun part starts, driving blind and engineering.
Do you see this picture? here I show the bits of the bridge as they will be seen from under the water -the place where those will be cut will be the water level.
Next I have been building a plastic box that I have been "gluing" on a small glass sheet. then with modeling paste for kids I place the soldiers and the bottom of the bridge. face down. i also have been cutting the tips of their hands for further use
So if you flip the diorama on the other side, that what you see: