The new Atomic Aquatics SV Contour Series Snorkel truly redefines how a snorkel works and helps divers extend their adventure. This Super Advanced Snorkel features: Atomic quality The Atomic Aquatics Scupper Valve snorkel design is based on the same principle as the one-way Scupper Valve used in boats Just like the one-way Scupper Valve on a boat, the lower section enable water to be easily expelled. 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 The flexible lower section drops the mouthpiece out of the way when not in use Posi-lock flex retainer secures flex section and mouthpiece Dual silicone mouthpiece prevents over-clenching of teeth that would restrict air flow Rotational mouthpiece with ratchet indicators Quick disconnect snorkel keeper includes 30 degree rotation Sliding snorkel keeper range adjuster allows for accurate placement without constant re-adjusting each dive This Fantastic snorkel is perfect for calm waters or for strong swimming situations!