quick question?

Has anyone used, worked with a scene that involved water. I don't mean a little I mean like say a "Creature From the Black Lagoon" kinda thing. I know I would really like to have a room with a path around a swampy type area that randomly bubbles like something is breathing underwater that would draw peoples attention for a pop up scare to come from the other direction. Think "Big Trouble in Little China" when they are in the sewer idea. Any idea how something like the water breather could be done? Also I would REALLY want to make sure it was safe so no one ends up either in the water/ slips and falls/ gets eaten kinda thing.