Every snorkel model in the SV Series utilizes the Scupper Valve on the bottom mouthpiece section. Then, Atomic gives divers a choice of tops to best suit their needs. The SV1 design has a conical flared top to deliver maximum airflow. The SV1 is the optimal choice for calm waters or for strong swimming situations. Even though water may enter the open top, the internal tube airway remains dry. Any water trapped below the mouthpiece is easily cleared with a small burst of exhaled air.