It was the cruise mystery that had our Premier perplexed last week: Why was the planet’s biggest private residential ship doing star-shaped bog laps in the waters off the Mid West?

Well, a spokesman for MS The World — which requires apartment owners to have US$10 million in assets — has finally revealed what it was all about.

The captain just wanted to have a bit of fun and run the crew through their paces, ordering they plot a course in the shape of a five-point star as part of a training exercise.

This is a recognised holding pattern that covers the maximum distance in the smallest possible area.

“The lay-up provided an extra training experience for the ship’s crew and added an element of fun," the spokesperson told 10 News.

The World originally arrived at Fremantle Port on March 13, hanging around Gage Roads until departing on April 6.

A planned trip to Exmouth could not go ahead after the Australian Border Force called on vessels to leave the nation’s waters.

Camera Icon The star-shaped route was part of a navigational exercise. Credit: Marine Traffic

Cruise ship passengers and their contacts represent about 40 per cent of all COVID-19 cases in WA and working out how to deal with a number of ships pulling into the State's ports has proved one of the biggest headaches throughout the coronavirus crisis.

Last week, Premier Mark McGowan said he was unsure why the ship was hanging around.

“The World left Fremantle four or five days ago, she’s in Geraldton doing laps, we don’t really know why she’s doing that but that’s what she’s doing … in open waters, so it’s outside our control,” the Premier said.

The World spokesperson said the ship had been "taken out of service" until July due to ongoing safety concerns posed by the coronavirus pandemic.

While no-one had tested positive to COVID-19 only a skeleton crew remained on board after all residents, guests and non-essential crew disembarked by March 20.