Many freedivers and spear fisherman differ on what technique to use when it comes to the snorkel. Should you dive with it in your mouth or out? And what are the dangers and benefits of each technique?
Some freedivers like to keep their snorkel in their mouth the whole time. Some argue that by doing this they are able to keep their face underwater the whole time whilst they are diving so that the snorkel does not disturb the sequence of dives. Others say that the snorkel wobbles less during the descent if it is in your mouth.
These reasons may be valid but personally, and I know other instructors are the same, I will always teach students to remove the snorkel just after your final breath as you start your descent. Why do I recommend this? Well, when you're freediving underwater with the snorkel in your mouth, the only thing stopping the water rushing into your lungs is your tongue which actively blocks the water from coming in your mouth. Were you to blackout underwater, your tongue would no longer perform that function and you would be introducing water into your airway.
Even if you were not to blackout, as you go deeper the negative pressure on your lungs can put strain on the throat. If the muscles around the throat were to give way even slightly, then you would be essentially sucking in water. But if your mouth is also closed, then your mouth would act as a critical barrier.
Do you dive with a snorkel in or out?