On TV, a diver walks out onto a platform. The camera fixes on him. He waits. He leaps. And then — somehow — the camera stays with him as he plunges. In the instant it takes him to break the water’s surface, the picture suddenly cuts to an underwater shot — and we watch in disbelief as the dive culminates in a burst of bubbles.

How do they do it?

Well, there’s a rope. There’s a pulley. And the rope and the pulley work a contraption made out of a pipe. The whole gizmo is based on the brilliant insight that objects fall at the same rate regardless of mass. A Tuscan by the name of Galileo came up with it about 400 years ago; if he were alive, he’d call it cutting edge. And there’s the beauty of it: It’s sophisticated, yes, but only because it’s simple.
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Garrett Brown revolutionized the movie business 38 years ago when he invented the Steadicam, a mechanical arm for cameramen that smooths away the jerkiness of hand-held shots. Much later, he came up with the Skycam, which rides a web of wires above the heads of football players. In between, Mr. Brown, 66 years old, got his one-line brief from NBC: “They wanted a camera,” he says, “that stayed with divers, including going underwater with them.”
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The falling camera rides a rail on the inside of the pipe. A glass strip runs along the pipe’s full length; the camera takes its picture through the glass. From the diving platform to the water line, the glass is smoky. Below the line, it’s clear, so the camera need not adjust its exposure as it streaks into underwater darkness.

The pipe is caulked. The camera drops through air. “It doesn’t splash into the water,” Mr. Brown said. “That would look horrible.”