Cool, now you need to replace it. It's a pretty important part. When there is no exhaust coming out of the engine that flapper shuts the exhaust tube and prevents a swell or wave from pushing water up into the engine.
Run without it, get stranded, replace at the very least the head of your engine at $800 in parts alone. If you have a 3.0L 4 cylinder, they aren't terrible to replace, once you get into the V8s though, real PITA.