Can someone please explain to me what is the difference between a Lotus flower and a Water Lily?

I understand that Water Lilies lie right on the water, while Lotuses are a few inches above water. Do they look exactly the same? I kept comparing and contrasting between the two with google and pictures, and I think they look similar and some looks different. I am really interested in knowing whats the difference, especially if they look the same. Just like alligators and crocs, i can't differentiate them.