[The author of this passage, William Finnegan, describes an experience surfing in very high waves off Ocean Beach in San Francisco. Only the very bravest and most experienced surfers attempt these waves in the winter. As the passage begins, the author and a friend have paddled out but were still too close to shore when a huge set of waves trapped them inside.]

(1) The first wave snapped my ankle leash--a ten-foot length of polyurethane, strong enough to pull a car uphill--as if it were a piece of string. (2) I swam underneath that wave and then kept swimming, toward the open ocean. (3) The second wave looked like a three-story building. (4) It, like the first wave, was preparing to break a few yards in front of me. (5) I dived deep and swam hard. (6) The lip of the wave hitting the surface above me sounded like a bolt of lightning exploding at very close range, and it filled the water with shock waves. (7) I managed to stay underneath the turbulence, but when I surfaced I saw that the third wave of the set belonged to another order of being. (8) It was bigger, thicker, and drawing much more heavily off the bottom than the others. (9) My arms felt rubbery, and I started hyperventilating. (10) I dived very early and very deep. (11) The deeper I swam, the colder and darker the water got. (12) The noise as the wave broke was preternaturally low, a basso profundo of utter violence, and the force pulling me backward and upward felt like some nightmare of gravity. (13) Again, I managed to escape, and when I finally surfaced I was far outside. (14) There were no more waves, which was fortunate, since I was sure that one more would have finished me.

--William Finnegan, "Surfing," The New Yorker

1			What are the two characteristics of these waves that the author emphasizes in the paragraph?
2			In sentence 1, Finnegan compares his ankle leash (the device that anchored his ankle to the surfboard) to a piece of string. What does this comparison suggest about the first wave?
3			What is the simile in sentence 3 meant to emphasize?
4			Explain what Finnegan means in sentence 12 by the phrase "like some nightmare of gravity."