I think that one of the biggest problems students have with mask clearing is that the "official" instructions for how to do it are not really appropriate to the way it is traditionally taught.
By this I am referring especially to the instructions to tilt your head back. The idea is that a diver who is diving in a normal horizontal position needs to tilt the head back to get it to a vertical position so that the water will run out the bottom of the mask--the lowest point. If a diver who is diving in a normal horizontal position does not tip the head back, the inside of the mask will be the lowest point, and water will stay trapped in it.
Unfortunately, these skills are usually introduced to divers who are kneeling in a vertical position. That means that the head is already in a vertical position, with the bottom of the mask the lowest point. Tipping the head back is unnecessary. In fact, tipping the head back to an extreme can be very counterproductive. Teaching mask clearing in a kneeling position allows the diver to clear the mask with poor technique, and it is harmful to learning good technique.
I saw this clearly when I stopped teaching any skills on the knees and instead had students in a horizontal position, lightly buoyant, on the pool floor. When you see how dramatically different skills are when done in a true diving position, you can never go back to instructing on the knees.
By this I am referring especially to the instructions to tilt your head back. The idea is that a diver who is diving in a normal horizontal position needs to tilt the head back to get it to a vertical position so that the water will run out the bottom of the mask--the lowest point. If a diver who is diving in a normal horizontal position does not tip the head back, the inside of the mask will be the lowest point, and water will stay trapped in it.
Unfortunately, these skills are usually introduced to divers who are kneeling in a vertical position. That means that the head is already in a vertical position, with the bottom of the mask the lowest point. Tipping the head back is unnecessary. In fact, tipping the head back to an extreme can be very counterproductive. Teaching mask clearing in a kneeling position allows the diver to clear the mask with poor technique, and it is harmful to learning good technique.
I saw this clearly when I stopped teaching any skills on the knees and instead had students in a horizontal position, lightly buoyant, on the pool floor. When you see how dramatically different skills are when done in a true diving position, you can never go back to instructing on the knees.