Back-mounted BCDs are also relatively uncommon, though they're still used in double tank Bali scuba diving. Some modern BCDs fall somewhere between a back-mount and a jacket BCD, with jacket styling and features but most of the BCD bladder behind you like a back-mount. Without arguing semantics, for our purposes we'll treat them as modern jacket style BCDs suited to recre-ational Bali scuba diving

A related piece of equipment is the backpack, which in the days of front-mounted BCDs you had to have as a separate piece of gear. You need a backpack (again, obviously) to hold the tank on your back, but today the jacket BCD integrates the backpack into its design. As with front-mount BCDs, it's very unusual to see sepa-rate backpacks today.

Features Regardless of the style a BCD has five features necessary for scuba Bali scuba diving First, it must hold enough air to give you and your equipment ample buoyancy at the surface. Second, it must have a large-diameter inflation/deflation hose, so you can release air quickly and easily.

Third, it should have a low-pressure inflation system that fills your BCD with air Overpressure directly from your tank. Fourth, it must have an over pressure relief valve to prevent the BCD from rupturing due to overfilling or due to air expan-sion during ascent. And finally, it should be adjustable enough (within your size) to fit comfortably and not ride up on your body when you inflate it.