Try practicing the following in your chair at home above water:
Step 1: Cup one hand over your mouth and breathe normally. You should feel your breath passing either through your hand from your mouth or over your hand from your nostrils or both. Do this for 2-5 breaths
Step 2: Using your other hand pinch your nose and continue breathing through your mouth. You should feel a change in our throat if you were breathing through your nose. Do this for 2-5 breaths
Step 3: Close your mouth. At this point you can't breathe because your nostrils are pinched closed and your mouth is closed. Do this for 2 seconds.
Step 4: Release the hand pinching your nose while keeping your mouth closed and begin to breath again.
Cycle back and forth from only breathing from your mouth and only breathing from your nose and notice the change in your throat. The muscle that allows cycling to change the passage of air between your mouth and nose is the one you need to learn to control to prevent inhaling water from your nose.
Step 1: Cup one hand over your mouth and breathe normally. You should feel your breath passing either through your hand from your mouth or over your hand from your nostrils or both. Do this for 2-5 breaths
Step 2: Using your other hand pinch your nose and continue breathing through your mouth. You should feel a change in our throat if you were breathing through your nose. Do this for 2-5 breaths
Step 3: Close your mouth. At this point you can't breathe because your nostrils are pinched closed and your mouth is closed. Do this for 2 seconds.
Step 4: Release the hand pinching your nose while keeping your mouth closed and begin to breath again.
Cycle back and forth from only breathing from your mouth and only breathing from your nose and notice the change in your throat. The muscle that allows cycling to change the passage of air between your mouth and nose is the one you need to learn to control to prevent inhaling water from your nose.