The popular bail-out bottle known as Spare Air has evolved over the years into a fourfold defense system against out-of-air emergencies. Most divers are familiar with the original 1.7-cubic-foot model and the larger 3.0-cubic-foot model that comes in both air and nitrox versions. The latest to hit the list, however, is a tiny 1.1-cubic-foot gem that's prized by all types of water-sports enthusiasts. Mounted horizontally on a neoprene vest, it rides high on the chest and can be used hands-free. Free-divers, kayakers and big-wave surfers are all discovering that it's one piece of safety gear they simply can't spare.

MSRP $249-$320 www.spareair.com