Chrissie runs along the top of the sand dune with the boy in pursuit, the low angled camera tracking them both. The girl races out of the frame just as she cries out the word 'Swimming!' When the boy stumbles for the first time there is a cut to a second faster tracking shot of Chrissie, who, ignoring his pleas for her to slow down, takes off her blue windcheater and tosses it to the ground. There is a cut to a tighter tracking shot of the boy as he calls out 'I'm not drunk' and then the camera is back following Chrissie. Without breaking stride, she lifts her right foot to remove a sneaker. As she looks back laughing there is another cut to the boy. He is now running on flatter ground between two rows of sagging fences. His cry of 'I'm coming' is slightly muffled as he struggles to remove his sweater. There is a cut to Chrissie also removing her sweater before she runs topless away from the camera. The boy's repeated cry of 'I'm definitely coming' carries an obvious sexual connotation: his drunken pursuit of the girl is a kind of clumsy foreplay that ends with his tumbling uncontrollably down the slope of the dune into the white surf - an action, taken together with his repeated line of dialogue, that could be seen as a kind of premature ejaculation. Chrissie is seen as a naked wide-hipped silhouette racing into the sea, which glistens in the moonlight.The camera cuts back to the boy on the beach, still struggling with his sweater. He totters in the surf, trying to remove a shoe, laughing and speaking to himself.
The chase along the sand dune is executed with verve and economy through a combination of cutting and camera movement. After the first establishing shot neither of the characters appear in the same frame, thus emphasising the nature of the pursuit. By shooting the characters through the slats of the fence Spielberg was able to give an additional dynamism to the shots. Just as still images seen through the slits of a spinning zoetrope can give the impression of movement, so figures in motion filmed through vertical gaps can appear to be moving faster than they actually are. John Milius used a similar technique (which he acknowledged he had learnt from watching Kurosawa's samurai movies) for the opening attack of Arab horsemen in The Wind and the Lion.
Spielberg also manages some sleight-of-hand with clever cutting. We see Chrissie remove one shoe and so there is no need to show her take off the second. As she runs down to the beach she is still wearing her denims but when the camera cuts back to her seconds later she is naked. Strictly speaking the time that elapses between the two shots of her (one partially clothed, the other naked) would not be enough for her to struggle out of a pair of tight-fitting jeans, but of course it's totally irrelevant.
Editing allows a film maker to expand or compress time to suit their needs. Next time you watch a movie involving a time bomb (the Fort Knox climax in Goldfinger, for example) count down the seconds from the first shot of the clock and you'll see what I mean. Spielberg had fun stretching out of tension in the climax of the opening scene of Raiders of the Lost Ark, deliberately elongating the jungle creeper Indy clings to and slowing down the closing tomb from shot to shot. Here he was exaggerating editing technique to get a laugh, but in Jaws he used it to propel the narrative forward without snagging it on unnecessary details.
