The idea behind Simply Lowered Drawbridges is that all of the raised drawbridges should be replaced with the lowered version. It is an extremely simple mod that will allow you to get across the bodies of water the raised drawbridges loom over without having to either jump or swim around.

All you have to do is download this and drag the contents of the mod into your game's “Data” folder. The next thing you need to do is to activate the mod with your favorite mod manager. You will then be able to see the new bridges that have been created.