We are trying to plan my harbor water feature. But we also need part of it to be a trap door, not a pop out, that will swing down and out of the way, so I can get into the layout for any problems, like derailments. We are installing my LIONEL swing bridge to this situation. Any ideas as to putting the bridge down on the bottom of the river bed first, or on top of the water once poured? When we can find a sea wall, I am thinking the sea wall will hide the trap door on three sides, and the bridge will hide the seam/crack from view. Somehow a LIONEL tug will be nestled in a small slip as well. HELP!