For scuba divers, it's key to your certification that you understand how barotrauma works, what it's doing to you, and how you can avoid it. Divers have a much higher danger of other types of barotrauma, because going underwater also involves a difference between the air in your lungs and the pressure of the water outside you. If you're having lung problems -- chronic ones like asthma, or even just a cold -- you're going to have more trouble regulating that pressure.
As a diver, you're cautioned never to hold your breath, because it could cause your lungs to balloon up, essentially, which can be incredibly painful and cause real damage to your respiratory system. While pulmonary barotrauma such as this can also take place to a lesser degree, resulting in minor symptoms, it's still damaging. Remembering not to panic -- and resisting the urge to take large gulps of air -- is another part of the training, which also includes some hard-and-fast rules: Never hold your breath underwater, ascend fewer than 30 feet (9.1 meters) each minute, and always keep an eye on your air supply.
In fact, because of the weight of water and the mathematics of underwater pressure, you're in more danger -- both going down and coming up -- the closer you are to the surface. It may seem counterintuitive, but that's why it's so important to be educated: It's not about the depth, or the weight of the pressure, just the difference in pressure as it affects your membranes. There's a much steeper change in that pressure the closer you are to the surface, which means your membranes are dealing with more changes, occurring faster, as you begin your descent or finish returning to the surface.