I can see you having some water left in your mouth but I am not quite sure why you are left with a mouth full of water after you push the purge. Were you keeping your mouth sealed around the mouthpiece. If not, you could have been clearing the reg but water would fill your mouth back up afterwards. Make sure you keep a good seal around the mouthpiece when you press the purge and I would suggest that you place your tongue lightly against the back of the mouthpiece. That not only keeps you from shooting water into your throat but it also allows you to sip air without inhaling it. It is also a technique used for snorkeling. It could take a couple of presses on the purge...or forceful exhalations to clear the reg so putting your tongue against the back of the mouthpiece will keep residual water left in the reg from being inhaled.
I am trying to picture what could keep your mouth full of water but the only thing I can think of is that you are not keeping your mouth sealed around the mouthpiece.
Don't let it discourage you from continuing to pursue your certification. Many, many students have problems with any number of skills but most overcome them. I am sure there is a simple solution to your problem...Don't let it get you down....
I am trying to picture what could keep your mouth full of water but the only thing I can think of is that you are not keeping your mouth sealed around the mouthpiece.
Don't let it discourage you from continuing to pursue your certification. Many, many students have problems with any number of skills but most overcome them. I am sure there is a simple solution to your problem...Don't let it get you down....