In "Sharpe's Trafalgar" the titular protagonist travels on a British navy ship of the line and we get various descriptions of the cavernous bowels of the ship, filled with fetid airs and scurrying rats - as well as this line:
"Cowper, the purser, who normally stayed mole-like in the lower depths of the ship..."
Which immediately makes me think that in a fantasy age of sail, dwarves or goblins at sea would take on the below deck work.