(ETA: Allow me to quibble!
I'm sorry, I haven't read Challengers of the Unknown or really know anything about them, but your list of their names and "professions" seems to pretty easily map to the four elements.
Ace ( a pilot) = air (he flies for a living)
Red ( a daredevil) = fire (his name, daredevils tend to be "fiery")
Rocky ( a boxer ) = earth (his name, boxers are "rooted")
Prof (a marine scientist) = water (he studies life in the water and you mentioned he's a diver)