Newcomers to the concept of holidays at sea can be forgiven for imagining every cruise ship is a "luxury" vessel, given that today's cruise ships are the descendants of the grand ocean liners.

But the reality is that cruise ships, like hotels, come in all sizes and standards, and are designed to appeal to a wide range of budgets and tastes.

Some ships are perfect for honeymoon couples and youngsters in search of a lively holiday; others are better suited to travellers with youngsters in tow or to older people seeing the world a deux.

With their fantastic range of "floating resort" facilities, the Caribbean's collection of 2,500-passenger-plus mega-ships provide the ultimate all-action arena for young (and the young-at-heart) party animals.

But those who like to take life a little more gently may find a Mediterranean cruise aboard an older, more traditional ship more to their taste. If you prefer a taste of adventure, then try a sailing ship, or an ice-hardened adventure vessel. Or a cruise to the glaciers of Alaska, America's "last Wilderness".

Most of these ships will offer an element of luxury, in the shape of state-of-the-art facilities, nicely cooked meals, attentive waiter service, cosy bars and well stocked libraries.

But - and it's a big but - there's a world of difference between the little luxuries of ordinary cruising and true luxury cruising. If it's the real McCoy millionaire-on-sea treatment you're after, there are only a handful of cruise lines which really come up with the goods.

For the essence of real luxury cruising is that it provides four essential things ; space, exclusivity, top quality service, and lack of hassle.