This is a buoyancy compensator device (bcd). It is used to control your buoyancy underwater. In newer bcd's you can put your weights inside of it.

This is a mask, it is used to let you see underwater. It works by making an air space between the glass and your eye, it allows your eye to focus.

These are fins, they allow you to move underwater. There are many types of fins such as split fins, full foot fins, and booty fins. I like the booty fins best.

These are your neoprene gloves boots and wetsuits. They keep you warm and sometimes dry. If your doing cold diving you'll definitely need these

This is a snorkel it is used in emergency situations like if you run out air you go to the surface and use a snorkel to swim to the boat.

These are your regulators and computers. They let you breath underwater and they tell you how much air you have and how long you can stay under water according to your depth