"Sparkys" were electricians.
I was "Sparks" - the Radio Officer. Very often shipmates didn't know my real name - SPARKS wanna beer?
Crews from the sub-continent usually called us Marconi Sahib: Chota - little) for the Junior R/O, Burrah (= big) for the Chief R/O.
I also remember with amusement the Goanese steward coming in with the menu and stating there was "Marconi Cheese"!!!