1.   Drew said rescuers have been tapping in rhythm on steel or concrete, hoping for taps in response.

2.   He said two days before he was freed, he had heard rescuers tap three times on the rubble pile.

3.   He was found when rescuers tapped on the hull of his yacht and he tapped back.

4.   The six navy rescuers tapped on the hull.

5.   The rescuers tapped on the hull of the boat, and were elated when they heard tapping back.