To him pulling the mask off was like the movies, when they kick a male in the nuts, routine, obvious, the opponent would instinctively know it.
To my friend the challenge was how to kill or disable your under water threat.
I assume they both are underwater fighters so they are starting at similar places.
Went through the SFUWO, now Combat Diver, course in 1975. Still using the Emerson Rig for closed circuit back then.