Patek Philipe launched the Aquanaut range in 1997 as a lower-priced alternative to the existing Nautilus range. A true sports watch, the Aquanaut features a rugged three-part case and screw-down crown for 120 meter water resistance, the most of any watch with a sapphire caseback at that time. The original Ref. 5060/5066 Aquanaut was joined by a "Jumbo" Ref. 5065, with a 38 mm case, soon after, and both were replaced by the updated Ref. 5167 in 2007. But the Aquanaut had always been a simple watch, with a date window being the only complication.
In 2011, Patek Philippe introduced the first complicated Aquanaut model, this Ref. 5164 “Travel Time”. Like other dual timezone watches, it features a fourth “skeleton” hour hand that always shows “home” time while the main hour hand adjusts in 1-hour increments to show “local” time. This is done using buttons on the left hand side of the case, the bottom to more the hour forward and the top to move it back. Two apertures in the dial just below the centerline serve as day/night indicators for both home and local time. The date follows the local hand and is indicated with a pointer in a subdial at 6 00 rather than the window at 3 00 common to other Aquanaut models.
The case measures 40.8 mm, a little larger than the more-common Ref. 5167. A sapphire display caseback shows the same basic movement, Cal. 324, as that model but this complicated variant is known as Cal. 324 S C F US. The Aquanaut Travel Time is not available with a steel or gold bracelet as other Aquanaut models are.
A special version of the Aquanaut Travel Time was produced in limited numbers in 2017 as part of the Patek Philippe Advanced Research effort. Ref. 5650 featured a simplified mechanism for the second time zone which used the crown rather than buttons. Another unusual aspect was an open heart dial. Just 500 were produced.