I liked the article, but its author described Bob Butler (the person who first discovered the cannons) as an «amateur diver.»
Because the word amateur has a number of meanings (including the idea of unskilled),
I believe its use should be limited to times when it is both appropriate and necessary.
For Mr. Butler to have found them, I have no doubt that he is very skilled and professional in his diving and
he should be highly credited for doing this both voluntarily and without pay,
and for that, he has my full respect.