Calypso, Cousteau's old ship, was a liveaboard. With it, the founder of aqualung diving roamed the oceans on a lifetime adventure. For us, adventures of a lifetime are more likely. Our escapes from the real world are usually all to brief. But the attractions of basing your diving vacations from a liveaboard are just as persuasive, if not more so, than when Calypso first set sail under the good captain's command in 1951. Half a century on, the world is a very different place. Cheap air travel has opened much of the world to mass tourism. In the sixties just to dive in Spain from the UK justified not just tales of adventure in diving magazines, but even whole books! In the early seventies diving in the Sinai was still in its expeditionary phase and often took place under canvas. In 1976 the first tourists to come up with $7500, plus airfares, got to dive with the Great White Shark. Today Spain is principally a fall back for the diver towing a young family behind and diving on sufferance. A Hilton rises over Sharm El Sheik (and a Ritz-Carlton and a Holiday Inn and a Four Seasons). Day trippers exchange fifty quid for half an hour with whitey. There are more divers than ever before. To many economies, diver bucks are essential and to snare them a whole business infrastructure has moved in. Luxury hotels, fleets of day boats and chains of dive centres supply every demand. Almost. What they cannot always do is get you to the best locations or provide the maximum amount of actual dive time. And, oftentimes, they cannot get you away from that most despicable tribe - other bloody divers... Liveaboards go a long way towards overcoming the downsides to being shore based. The best diving locations can be to far from land for day boats to reach. Or at least far enough away that you can slip in and out of the water before the hordes arrive. Sometimes that fact makes them the best dive sites. Take the wreck of the SS Thistlegorm in the Egyptian Red Sea. Early morning sees an armada of day boats ploughing over the horizon towards this most famous of shipwrecks. And shortly after, a massed navy of divers descend upon her at once. Diving the Thistlegorm from the liveaboard Coral Queen made our dives very different. Guido Shariff, the luxury vessels owner, ensured we got our first dive in before breakfast. And by doing so we beat the crowds and had the wreck to ourselves. By staying out at sea, Guido could be on station much earlier than his Sharm locked competitors. He also knew which days the hordes travelled on, so we dived on a popular changeover day when there were fewer people on the water.

Other top locations may very well be beyond the cruising range of a day boat. Even if fuel supplies allowed, the boat could never make it out and back in one day. Liveaboards then provide the only option.

Liveaboards are often the most efficient way to dive. They can travel to a new location during meal breaks and many steam by night. This is very time efficient and can let you make more dives in a day or visit more locations than would otherwise be possible.

Like hotels, liveaboard boats vary in the standards of facility that they offer. Boats aimed at local club markets, such as those running from UK ports or overseas destinations like California, can be quite basic with bunkroom accommodation. Those aimed at divers from overseas are usually better appointed. It's usual to have private cabins with ensuite facilities. Methods of diving also vary with the location. Some boats will anchor up and then expect you to navigate back to the anchor line at the end of your dive. Others will come and find you. It's also common for liveaboards to act as mother ships to smaller, faster more manoeuvrable boats, such as rigid hull inflatables (RIBs). These are used to ferry divers to areas that the main boat might have trouble getting to, such as in among complicated reef passages. They also serve as recovery craft, collecting divers as and when they surface. Some liveaboards operate in tandem with dedicated dive vessels. The liveaboard serves as the base for accommodation, eating and general recreation. A second boat, which accompanies the main vessel, is the actual hub for diving. All dive gear is stored on board and tank filling, which can be noisy, takes place out of earshot. Liveaboards are often the venue for specialist diving activities. These can range from workshops on wreck diving, stills photography or video production through to special charters to encounter great whales. Often these will be taught or hosted by specialists in their field. It's also common practice for regular instructors to take their students on dive cruises to complete training begun at home and to run advanced, rescue and continuing education courses.

A few liveaboards are home to a group of elite specialists. For divers with a serious interest in a particular location or animal, these are the individuals and boats they will seek out. Diving is a very small world and it's not unusual to find yourself sharing your charter with professional underwater photo-journalists and television crews pursuing the same goals.

The liveaboard dive trip is usually excellent value. Choose wisely to ensure a safe boat, good food and great divemasters and you'll often find it cheaper than staying ashore, especially if you calculate the overall cost per dive.

Safety must always be a concern when selecting your boat. Regulations are often not as stringent overseas as back home and may not be enforced. Not all boats have life rafts for example. Some safety issues are raised in the Diver Magazine feature Dead Calm. Once you've experienced the sheer pleasure of a liveaboard vacation, you'll understand why Commander Cousteau took to the waves so completely.