Just like any other cooling system in a car: radiator and single fan belt are the key components.
Apply directly through the cruise ship managing company's website usually. Sometimes there are also agencies that recruit specifically for this specific niche of the leisure sector.
Yes, steer clear of them. I used one once and she turned out to have given me syphilis. When my wife found out she told her family and they beat me very severely so don't do this please, for your own sake.