If you were to win the lottery tomorrow, after you had promised not to change your life in any way at all, my bet is that pretty soon, you would start to wonder what are the greatest pleasures that money can bring?

After various purchases had gone tragically wrong, you would, undoubtedly, buy an ocean-going yacht, staff it with a smiling infallible crew, equip it with a first class chef, a heavy-handed barman and ( this is an extra which I beg you not to forget ) a small exquisite Thai spa.

You would request the Captain to sail around the Mediterranean and Adriatic, calling in at little-known exquisite ports and mooring up just far enough out to take in the view, but convenient for an easy run ashore in the ship's tender which would apparently have nothing to do but ferry you in and out all day.

If you felt playful you would go to the back of your ship and mess about in a sea kayak, a sailing dinghy, or a jet ski, watched over, all the time, by safety-qualified staff. Or you would dive off the deck into the perfectly clear sea and swim in the refreshingly cool salty waters.

In the evenings you would dine ashore, or you would eat topside on the highest deck of the boat, under the stars; or in the luxury of the silver-service dining room, or - I am not kidding here - you could summon a "champagne splash" a little mini-party just for yourself, when waiters would bring you champagne and caviar to the beach of your choice and serve it to you, complete with silver spoon, in the waves.

At night you sleep in your luxuriously appointed cabin with a sea view, or you can choose to sleep on deck, in a double bed made up with the best linen sheets, under the gently rocking stars as the ship sails to its next destination.

Now: the really good news. You don't have to win the lottery to have all of this. You can get this experience by the week : the Thai spa, the champagne splash, all the razzle-dazzle and glamour of a private yacht with none of the worry of mooring charges or fretting about the sonar.

How can this be? Let me introduce you to the magic that is Sea Dream Yacht Club, a near-miraculous concept based on the belief that a holiday cruising on board a yacht should feel just as if you are the owner, on your own private yacht. Itineraries are flexible, dress is casual, you can be as social or as lonesome as you like. The crew outnumber the guests, and luxury is the norm. There is an entertainments manager; but her job is to suggest things that you might like to do, and to enquire pleasantly afterwards if you enjoyed them. Everyone urges you to suit yourself.

There is no question of being roped in to some unwanted team activity, and anyone sleeping on the sundeck will be disturbed only by the whispered offer of a chilled drink from the bar which is open all day long and free. There is a casino : a tiny table which opens with quiet modesty after dinner and closes after mild excitement in the early hours. I have a hunch that quite a lot of money changes hands, but there was no ostentatious whooping or hollering about it.

There is a pianist in the little bar, who cannot stop you singing if you insist, and you will meet him during the day, helping you into the sailing dinghy. The Thai spa (which, when you are commissioning your own yacht you must take particular care not to forget) is simply out of this world. You can be wrapped and stretched and pummelled and stroked in a blissful miasma of perfumed oils by pleasant women with the hands of angels.

Better still you can enjoy this in the cool shadows of a treatment room with the taped soothing sounds of waves, or you can go on deck and be stroked by oils and wafted by the Adriatic breezes with the sound of the real thing. It is heaven.

It feels like a privately-owned yacht because indeed, it is just that. On our voyage the owner, his friends, and his family were aboard: blond-headed children, smiling mother, three generations of them. Le Patron sails here, in fact. It gave the voyage an even more friendly feel, since many of the guests were either friends or colleagues. Commendably, you would never have spotted the owner by the service he got. He was drenched in the same luxury and treated with the same pleasant helpfulness that we all experienced. And, to be honest, on one occasion I am pretty sure I got more pudding.

The Sea Dream's route this summer is from Venice down the coast of Croatia to Dubrovnik, or you can take the voyage in the opposite direction. The older guests on board told me that the countryside of Croatia was like the South of France before the boom in tourism and development, and I could see that the bleak beauty of the coastal landscape interspersed with enchantingly pretty ancient towns must be just like the Mediterranean more than fifty years ago. The little towns offer charming small pleasures: this is not a holiday for either night-club owls or history groupies. It is a trip with small pleasures. You can take a trip to a vineyard, a walk in the country, or stroll around a museum or a monastery. We took a horse ride which was a pleasant amble by a coastal path in dazzling sunshine beside a sea of exquisite deep blue, and in the two hours we never passed another soul.

We went on a vineyard excursion to a tiny family-owned vineyard and were welcomed with tremendous warmth and charm to taste some of the worst wine I have ever smiling agreed was very tasty! Very rural! The Dutch bought gallons of it, and the Americans shipped it home for gifts. The final port of call of Dubrovnik is the most fashionable and popular city on the voyage after Venice. It offers restrained hustle and bustle, and also the rare beauty of an ancient walled city set in a sparkling sea.

There are moments when it is as spectacular as any film set, the golden walls of the city reflecting in the clean water are too beautiful to seem real. There are wonderful quayside restaurants serving fish which is delivered by the fishermen to the chef at the waterfront back door as you sip your aperitif at the front, there are old buildings in honey coloured stone and everywhere there is music: buskers and mini-orchestras, set up on the corners of squares and playing to the darkening sky. It is a city recovering from war, one of the museums records with quiet sorrow, mediaeval arrowheads next to a mortar shell; and yet it is a city of such gaiety and harmony that it is impossible to think that there can have been hatred here.

The greatest praise for the cruise from Venice to Dubrovnik is that you leave the ship with deep regret. The only wish is to stay on board and go all the way back again. It is a beautiful coast and a cruise is a perfect way to enjoy it: Rollover bonus ball, anyone?