Passengers boarding a Carnival cruise ship are promised a world of endless food, relaxation and oceanic luxury.A once-in-a-lifetime opportunity to explore the world by sea.But for the crew who make these luxury escapes possible, life is vastly different.An ABC News investigation has uncovered allegations of workers forced to eat rotten leftovers, extreme working hours and medical neglect on board the ships of the largest cruise company in the world.Carnival corporation operates over 90 ships globally, with around 100,000 crew on their ships at any one time. (ABC New: Pete Garnish)Workers paid less than $3 an hourCarnival Corporation has more than 90 ships, operating three full-time in Australia: Adventure, Encounter and Splendor.Crew working on Carnival's Australian ships told the ABC they work 12 hours a day, seven days a week for almost all of their nine-month contracts.Queen Onuoha, originally from Nigeria, worked as a beauty specialist for two seasons aboard the Carnival Adventure and the Carnival Encounter.She said she often worked 14-hour days and bought caffeine tablets to stay awake during shifts.Crew contracts seen by the ABC show that some workers are paid $US23.26 ($AU33) a day.