Tides come in, tides go out. You can't explain that.

This argument was made infamous by Bill O'Reilly on his show The O'Reilly Factor, in an interview with David Silverman, current president of American Atheists. It has been used by Bill in many other encounters with atheists, and has been ridiculed and parodied to the extent of becoming an Internet meme.

Bill is essentially saying, "we don't know how the tides come in and go out, it is therefore necessary to invoke god to explain this", which is a god of the gaps argument. The hilarious irony is that, unknown to Bill at the time, science had long ago explained how the moon's gravity causes the tides, and so the gap is non-existent. In a response to this explanation, Bill retorted "how did the moon get there?", which is essentially a crude uncaused cause argument.

In the same video response, O'Reilly asks "Why do we have a moon and Mars does not?" In fact, Mars has two moons, Phobos and Deimos.