Who invented the dive mask?

Answer 1

Not sure that there is a single definite "inventor". Dive masks of some description have been used since ancient times using polished tortoise shells over the eyes (ie. without enclosing the nose).

When Scuba diving became popular in the 1950s, most people simply made their own masks using a lense and either vulcanised rubber or neoprene. Modern masks only really started to develop when manufacturers stepped forward to make masks with finger pockets to pinch the nose to equalise.

I am not aware that anyone has ever held a patent in any country for "inventing" the dive mask.