A comfortable and good fitting dive mask is essential to prevent water from entering your mask. The silicone skirt of the mask creates a watertight seal with your face. The mask and/or the snorkel has as an optional feature a Blowoff valve, which makes it easier to clear your mask/snorkel.The fins are the diver's engine. Investing in a good pair of fins, makes the diver/snorkeler less tired, less usage of air and faster/easier movement in the water.