The SV2 FLEX has semi-dry top with horizontal vents engineered to diffuse splashed water that would normally freely enter the snorkel top. The small gaps between the vanes of the vent restrict water speed and droplet size and permit most of the splashed water to exit the special vents without entering the breathing tube. The end result is less water in your snorkel. The SV2 is perfect for rough or choppy water conditions.The flexible lower section drops the mouthpiece out of the way when not in use. The dual silicone mouth piece prevents over-clenching of teeth that would restrict airflow.