There are a few key pieces of equipment that required for any dive, and some other equipment that is used for more challenging diving conditions. Beginners and novice divers, however, will definitely need the following:

Mask
The human eye cannot see clearly through water so a pocket of air is    required to maintain vision when diving. A diving mask is like a large pair of swimming goggles with a silicone seal all the way round. It also includes a silicone pocket/seal for the nose, to prevent the wearer inadvertently trying to breathe through their nose and sucking in water instead. Diving masks are built to withstand the greater pressures found underwater, so a snorkelling mask is not suitable for diving.
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