On a mobile, human-made island floating south-south east of New York on the Atlantic Ocean toward the Eastern Caribbean a few weeks earlier in 2015. A brisk walk for a mile of rounds on a smooth deck just some feet above the liquid surface seems a miracle -- to be able to virtually walk on water.

For an insecure mortal, who prefers the solid earth beneath his feet rather than ephemeral depths, the brief exercise provoked recall of previous passages on ships -- as a child in the early 1950s with mother on the S.S. Sabarmati or the S.S. Saraswati on the short Bombay-Karachi-Bombay routes and, later in 1967, the ferry service in the Channel between England and France. Later still, on a yacht off the Malaysian coast or one-day-long trips out of the Karachi harbour or elsewhere.

But these steps in 2015 were the longest walks on one’s longest voyage to date on the blue beneath.

During the first three days of an eight-day adventure, no stops, only continuous gentle movement over the vast, azure ocean. Mostly calm. Occasionally mildly choppy. Mostly blue. Sometimes dark. Always awesome. An ultimate serenity felt in this part of what comprises over 70 per cent of the planet’s surface. This part of the 97 per cent of all the salt water we have. The immensity which humbles one yet again. But here so distinctly, into infinite humility. This realm seethes forever, ceaselessly restless. Like our minds, that conceal millions of circuits and secrets.

With a full circular 360 degree sweep by the eyes, there is only the sea one sees. No other object in sight, not another ship, no bird, no plane in the air. Only majestic, slowly rolling white clouds. And disengagement. From the familiarity of Karachi, and the lesser intensity of New York. From cell phones, cars, traffic, noise.

Yet as one strides across the decks of the vessel, human company and direct information there is aplenty. To start with: one’s own spouse. Proximity to her, not distance, lends a new enchantment to the view. Greatly missed daughter Mehreen, son Kamal Kadeer, daughter-in-law Zainab, grandson Zaka (all of 9 months young) who have thoughtfully together gifted us this wedding anniversary holiday.

Several friends have already made these ocean tours. As latecomers to this kind of travel, we are two, content to be by ourselves, but with many others, also presumably celebrating their respective milestones.

About 3,500 passengers. About 1,100 crew. Yet with 4,600 people travelling in a single boat there is little sense of being crowded. Enough options to find a quiet corner to be alone. Or join the rest. A microcosm of many parts of humanity. In largish tour groups. In smaller teams. Big families. Couples. Resonant with age. Newly-minted honeymooners. Even singles. Persons in wheel-chairs tended by relations. Special persons, including some who used crutches. A fine variety of ages, shapes, sizes. Some of them, particularly female, regardless of contours and weight, charmingly insistent on sporting bikinis -- these can become distracting diversions. Almost all continents and races represented.

There was Mr Carter, citizen of Jamaica, our own designated cabin attendant -- courteous, attentive, well-spoken. There were Mr Alvir from Macedonia, our regular waiter at dinner every night, with smiling Ms Chloe from Chile. Providing prompt service. Then, they join colleagues to sing melodies for guests.

On the last night on board, they aptly chose the golden song by Peter, Paul and Mary from 1970:  "I’m leaving… on a jet plane, Don’t know when I’ll be back again…".

Such large numbers of strangers in the night. And in the day, just as in a city. Anonymity and privacy, by choice, even when so close together -- a kind of collectively practiced unwritten code of restraint. No inappropriate attempts at familiarity. One can share the vessel with these thousands for over a week and yet come away without intruding or being intruded upon. Only brief interludes of polite pleasantries. Touching expressions of courtesy as in an offer of seats. But no need to offer visiting cards. Except once, to Farah and Ozair Barlas, a fine young Pakistani-American couple whose presence we enjoyed and with whom we shared some delicious meals. Ideal autonomy-on-demand -- the seclusion of the cabin. From the balcony one can dwell at length on how the sea forever seeks to meet the sky.

One never met the Italian Captain in person. But he was heard on the public address system, like a friendly Big Brother, on some occasions, to introduce himself or to convey new information. Easy-going, amiable Malcolm Burn, the American Cruise Director, hailing from the Bronx, was both visible and audible. He hosted the colourful evening stage shows and engaged guests with humour and banter. And made announcements through the PA (public address) system to highlight the day’s special programmes.

The S.S. Carnival Splendour is another name for a lively global city on the move -- in more senses than one. Through the water. And through myriad activities on board. With dozens of choices. Swimming pools and whirlpools. Spas and saunas. Fitness gym. Jogging track. Dancing courts. Music concerts. Casinos. Shopping galleries. Art auctions. Lectures on better living. Bingo games. Bars. Snack bars. Ice cream counters. Beauty salon. Boutique. Duty- free shop. Conference room. Teenage disco. Internet cafe.

Timed free meals in large restaurants. 24-hour free meals from two points. Free 24-hour room service. Paid-for food and drinks in restaurants and bars. Stand-up comedy routines. Evening stage shows in a 1,600-seat, tiered theatre with an orchestra pit that features spectacular entertainment. Audience-participated hilarity. Age-group segmented spaces that cover almost all groups, from grandbabies to grandparents. Sports. Games. Movies. Library. Photography studios and services. Nine categories of accommodation for passengers. Cabins with balconies. Cabins without balconies. Penthouse suites. Others. All with TV sets that bring news channels and packaged shows as also closed-circuit ship-related content. All rooms kept squeaky clean, serviced by attendants twice every day.

Multiple levels -- about 13 passenger decks (storeys). 18 elevators.

The cuisine was often superb, the range quite international. One counter was called ‘Tandoor’. Another specialised in pizzas round-the-clock. Whether the spread was on self-service shelves or specialities brought to the table, the selection was thoughtfully done, tastefully prepared.

There are other small details -- this ship-city was constructed in Italy at a cost of about $750 million. It was launched in 2008. Passengers pay a range of prices, depending on the choices they make. Booked well in advance, a cabin for two with an ocean view can be about $900 per person. But if vacancies remain in the last few days before a cruise begins, prices are slashed for those who can suddenly adapt their schedules. With each of five shore day-excursions selected from a range of over a dozen, the charge is an average additional price of about $80. Allowing for purchases of various items, services on board not covered by the basic price, the cost works out to about $2,200 per person, inclusive of an air ticket from the last port-of-call (in our journey, San Juan, Puerto Rico) to the place where the journey began; unless the route is a round-trip. (The above figure does not include say, the cost of a Karachi-New York-Karachi air ticket). At a daily cost of about $270 per person the price for the cruise is well worth the experience -- for those who can afford it! Or for those who receive a surprise gift!

There is obviously no upward limit for what can be spent -- the sight of hundreds who play casino games every night or keep alcohol bars busy or keep the shops humming reflect the turn-over that must greatly please the investors-owners.

To traverse a world of water for a week in luxury, to alternate between lots of company and activity and instant privacy is to discover new joys of travel. And to realise afresh the bounties of creative human capacity and the priceless treasures of Planet Ocean-Earth .