National Geographic : 1998 Aug
Hitching a deep ride Bottlenose whales spend only 15 percent of the day at the surface. To learn what they do in deep water, the team uses a crossbow and a suction-cup dart (above) to attach a time depth recorder (TDR), a palm-size device bundled with a float and a radio transmitter (above right). Finding targets is the easy part. Whales congregate over the deepest parts of the Gully (art below), a submarine canyon 235 miles off Halifax. Getting TDRs to stick is harder. After days of frustration a TDR was finally secured to a whale for 28 hours.