Two cruise passengers were left stunned after finding a member of staff having sex in their cabin.

Bobby, 64, and Mary Jackson, 62, were travelling with Norwegian Cruise Line from Singapore to Thailand on their dream cruise.

Just after boarding the ship, they were confronted with the sight of a naked male crew member having sex with a mystery woman on their bed, The Sun reported.

“I was horrified, what I witnessed was extremely unpleasant,” Mrs Jackson said.

“There was a man and woman having sex on the bed in our designated room.

“I immediately closed the door again.

“Eugene, our cabin attendant, was present and he immediately went to inform his supervisor.

“We are not prudes but this was ridiculous.”

The couple, from Northern Ireland, had paid about $AU8600 for the week-long cruise — their first ever — on the 2376-passenger Norwegian Jewel ship in October.

But the trip didn’t get off to the best of starts when they were left waiting on the quay side at Singapore’s Marina Bay for two and a half hours in scorching heat before boarding.

“When we finally got on the ship we first went to the bar for a drink because we were exhausted after all the standing around in the heat,” Mr Jackson said.

“We were then shown down to our state room accommodation, which we were really looking forward to seeing.”

When they got to cabin 10039, the electronic key card wouldn’t work in the door at first.

But at the third attempt, the door finally opened — and that is when their jaws hit the deck.

“I could see the back of a man on the bed who was directly facing us and it was obvious he was in the middle of having sex with a woman,” Mrs Jackson said.

“I shut the door immediately and we went into the cabin next door where my sister was staying while the staff sorted this out.

“I was traumatised and I needed a glass of water.”

The couple went to complain to the ship’s guest relations manager but there was no alternative room available because the boat was full up, they said.

“We went back to the cabin and tried to go back in there but although the woman had left, the male was still there,” Mr Jackson said.

“Two of the ship’s crew in white uniforms eventually persuaded him to leave. He looked very sheepish.

“I asked if the crew knew him and they told me he was a worker on the boat.”

The couple said they were “insulted” when they were then offered the equivalent of about $180 of credits to spend on the ship as compensation.

Things got worse when Mrs Jackson took ill with a stomach bug two days later and spent most of the rest of the trip confined to her cabin.

“I was extremely frightened because I was very sick and I was a long way from home,” she said. “The ship’s doctor put me on an IV drip, gave me antibiotics and I was told to stay out of the sun.”

When the couple returned home they wrote to Florida-based operators Norwegian Cruise Line to complain about their experience but were unhappy with an offer of $360 each in credits towards their next trip with the firm, if taken this year.

The cruise company Norwegian Cruise Line said a full investigation has taken place and the appropriate action has been taken.

They said the Jacksons have been contacted to discuss compensation.

Sun Online Travel has contacted Norwegian Cruise Line for comment.

This article originally appeared on The Sun and was reproduced with permission.