Heartbreaking moment when parents watch their children sail away on a cruise ship.

What was meant to be a relaxing holiday has become a nightmare for two parents who watched helplessly as a cruise ship with their young children on board sailed away before their eyes.

Spending seven days on board a cruise ship travelling between the US and the Bahamas last week, the family of four were separated four days in, after the mother failed to return from a land excursion on time while docked in Nassau.

After speaking with the ship’s captain, the father agreed to leave his two children — believed to be aged nine and 12 — with an uncle and leave the ship to locate his wife.

But by the time the mother finally arrived back at the port, the ship had already departed, with both parents then left stranded.

The mother sobs as a cruise ship with her kids on board sails away. Source: Youtube.

In a video filmed by a passenger on board, the mother can be seen dropping to her knees, pleading for the ship to return.

The cruise ship departed on 21 April, and did not make any additional stops between Nassau and its final port of call, New York, on 24 April.

Archie Pottinger, a spokesperson for the ship and parent company Norwegian Cruise Line, told the Daily Mail that prior to its eventual departure, on-board staff "went beyond normal protocol and waited an additional half an hour for the guest."

Cruise ships generally request all guests to be back on board at least an hour prior to departure on sailing days.

The children made the return journey from Nassau to New York with other relatives. Source: Google Maps. 

"When she had still not returned," Pottinger continued, "And following consultation with the family, it was decided that the husband would disembark with their travel documents to wait for his wife while the children would stay with their uncle and his family on the ship for the remainder of the voyage."

Pottinger said the company offered the parents accommodation and assistance with alternate travel arrangements to ensure they were reunited with their children as soon as possible.

The cruise ship was docked in Nassau prior to departing. Source: iStock.

One guest can be overheard on the video saying, "Go back and get 'em," while another admitted, "This is crazy. I didn't think they would do that."

"This ship aint even trying to slow down either," says Scott Thomas, the video uploader.

While the family was successfully reunited in New York, it is not yet known why the mother was so late in getting back to the ship.