Dive skins are the thinnest and lightest among the other types of exposure suits. They are worn mostly in tropical waters with friendly underwater environments, as they offer the least amount of protection. Dive skins are usually made of Lycra or some very thin neoprene and are only about half a millimeter thick. Many divers also wear dive skins under their wetsuits for easier donning and doffing.
Wetsuits provide better protection and allow to dive in a much wider range of environments. Thus, they are the most common type of exposure suits. Wetsuits are made from neoprene, a material that consists of tiny separate gas bubbles. The gas in these bubbles, as well as the rubber material itself, warm up from the heat of your body, providing thermal insulation. Note, that the air bubbles inside the wetsuit compress as you descend deeper and the water pressure increases, so the suit becomes thinner and provides less insulation. The deeper you dive (and the colder the water is), the thicker your suit should be. One more thing to note is that wetsuits come in many different varieties, styles and thicknesses. For example, the are two-piece (farmer John or Jane) wetsuits and one-piece suits, or as they are also called full suits, jumpsuits or steamers. Nowadays, thanks to their versatility, full suits are used more commonly.
Dry suits are used for cold water diving (50 degrees Fahrenheit or 10 degrees Celsius). As the name implies, a dry suit does not allow any water in and always stays dry on the inside. Unlike wet suits that come in various configurations, all dry suits are full body suits. Special waterproof zippers and latex or neoprene seals with large contact areas help to keep the suit truly dry.
Once you know what kind of suit you need, don’t forget to pick out such additional pieces of divewear as vests, boots, gloves, hoods, etc.