One piece of equipment you need is your mask. This is your window on the underwater world, so make sure it fits snugly and gives you a clear view. Over time a mask does tend to get scratched, so this is one piece of equipment you might not want to buy second hand. You also need a regulator, to help you breathe underwater. Basically, it takes the compressed air in your scuba tanks and reduces the pressure down to a level that is breathable. It only delivers air when you inhale, so that you don't waste the air in your tanks.

Another important piece of equipment is your buoyancy control device, or BCD. It's worn like a vest, and contains an expandable bladder that you inflate with air from your tank as you're diving. This is mandatory, because as you dive deeper, the water pressure increases. So unless you can increase your buoyancy at that point, you will start to sink like a stone.

Unless you're only diving in shallow, warm tropical waters, you're going to want a wet suit. This works efficiently to keep your body temperature at normal levels. The wet suit helps your body to deal with the increased water pressure at depths and also the colder temperatures. Some people are comfortable with a body suit, so that may suit you better. Either way, you end up with a skintight outfit that clings closely to your body.