The Blancpain Fifty Fathoms Flyback Chronograph ($13,700; 877-520-1735, blancpain.com) takes high style to new depths. Its 45 mm case and chronograph buttons resist water to three hundred meters, far below the ninety-one meters—fifty fathoms—of its 1953 archetype, which was developed for the French Ministry of Defense combat divers and also worn by Jacques Cousteau and his researchers. An outer mechanical bezel safely monitors time underwater, and the "flyback" function allows a new timing event to be started without having to stop and reset the hands.
The stainless steel Aquatimer Chrono-Automatic by International Watch Company ($5,500; 800-432-9330, iwc.com) is notable for its mechanical inner rotating ring: The crown at four o'clock adjusts the numbered ring for dive timing and also resets the chronograph function. Water-resistant to 120 meters, the self-winding IWC in a 42 mm case features a stainless steel bracelet or a rubber strap.
Breitling's Superocean Héritage ($3,120; 800-641-7343, breitling.com) updates the 1957 original—the new model is water-resistant to two hundred meters. The stainless steel Superocean features a unidirectional rotating bezel. As with the Blancpain and IWC, a luminous coating on the hands ensures easy reading in murky underwater conditions.