Is it cheaper to live on a ship than rent an apartment?

They didn't live on that ship year round, but changed cruises according to season and what interested them. They took three-month and six-month stints, Madame X said, although I was never really sure if they had a base home.

Madame X seemed to have a fine life. She visited the ship's hair salon every morning to have her extravagant beehive hairdo (very Marge Simpson) washed and set. She sat on the deck for long periods of time and had waiters fuss over her. Mr X was a bit of a grumpy sort and I could see she needed the attention of staff and craved conversation with strangers. He was probably a terrible grouch at home.

I assumed they were rich, but in fact it may have been cheaper for them to cruise round the world than run a house in New York, where they came from.

The next year, as I was boarding a ship in Sydney's Barangaroo for an inspection, I saw the same couple get off to go on a tour. You couldn't mistake her hair. He still looked grumpy.

I've always wondered what it would be like to live like this. The advantages would be round the clock service, the constant stimulation of new ports and new people to meet, and never having to make your bed, clean your bathroom or cook dinner.

The disadvantages, I imagine, would be claustrophobia, rough seas if they bothered you, boredom with the same meals and activities, a sense of disconnection from your family and friends onshore and no continuity of treatment with doctors and other professionals.

A few years ago I had lunch on board The World, the world's largest privately owned yacht. It contains 165 residences, apartments that range from studio size to three bedroom. It's effectively a floating apartment building and run like a co-op with residents making mutual decisions on the ship's ports for the coming year.

See: What it's like to live on a cruise ship for eight years

I had always scoffed at the idea. I couldn't imagine anything worse than being stuck on a big ship with a whole lot of unadventurous rich people in their twilight years. Not that I don't love spending time with my parents' generation but I did imagine the ship would resemble a massive, seaworthy retirement home.

Not so, in fact. There were plenty of young 'entrepreneurs' who owned apartment on the ship. Self-employed people who worked globally took advantage of all the ports to do business. I met an Australian couple who were retired but barely out of their 50s and actively involved in the art and music scene. They travelled the world going to concerts and galleries, indulging their hobby.

It didn't seem half bad, although I wondered what it would be like if you didn't get on with any of your fellow passengers. You couldn't get off and away from them at the end of the cruise.

The World is somewhat pricier than an $162.78-a-day cruise on the Arcadia but probably less than a harbour-front apartment in Sydney.

Still, a life on the ocean waves, without a home on terra firma, might put me all at sea.

See also: World's 10 biggest cruise ships

See also: Best cruise destinations in 2016