On a recent summer afternoon in Vouliagmeni, a marina half an hour's drive from central Athens, Captain Costas Karachalios proudly gave a tour of MadiBlue. Designed by John Bannenberg in 1986, the 47-meter yacht has been chartered by the Prince of Monaco and Princess Margaret, among others.

The master bedroom has both a hot tub and a sauna. Aft-deck, a waterfall trickles alongside the dip pool. Up front, several personal watercraft stand ready. There's even a helicopter pad on the sun deck. The yacht runs about €122,000 per week in high season (the Olympic-period price hasn't been disclosed). That includes a crew of 10 (one a chef), but doesn't include taxes, fuel, food or drinks. With those, the total would probably come to roughly €152,500.

Closer to Athens, in Mikrolimano ("little harbor"), the 31-meter yacht with the unlikely name If had just returned from a charter, and crew members were at work polishing the boat's already shiny white exterior. (Counting the chef, the crew numbers five.) Built in 1999, it is compact and modern, with Sicilian marble tabletops, a full kitchen and a master bedroom with a hot tub. On deck there's a personal watercraft and a retractable sunroof. The yacht sleeps up to 10, and costs about €58,000 per week during normal peak (non-Olympic) season.

Yachts can be much bigger, and much more lavish, than that. The 81-meter-long Omega, chartered by Citigroup Inc. for the duration of the Olympics, was completely refurbished in 2003 and has a studio for yoga and pilates, spa and library. It can accommodate 32 guests and carries a crew of 21. For the two weeks of the Olympics, the cost is about €415,000, according to the broker who chartered the yacht.

If you're a sailor preparing to charter a bareboat yacht, read the part of the contract that specifies size and type of boat with special care. Some may not be specific enough -- and you can get shortchanged. "Sometimes you'll find another yacht at the dock than the one you'd chartered, which is not a problem if this one is better," says Diederik Willemsen, who runs sailingissues.com⁵, a Web guide to charters and sailing on the Mediterranean. Most contracts mention legal terms such as "same size or bigger" or "reasonably comparable," he adds. "Needless to say, many yachts are one foot longer but should really qualify as wrecks."

Bareboat or fully crewed, the right size depends on the size of your party (and budget) -- and the size of the places you want to visit. Mr. Willemsen warns that the largest yachts can be difficult or even impossible to maneuver into some of the less touristy small islands. "It can really limit your itinerary," he says.

Your choice of destinations should also help determine whether you choose a motor yacht, sailing yacht or motor sailer. "Motor yachts are great to cover distances in a short period of time, which allows you to be very flexible in your itineraries," Mr. Willemsen says. Because sailboats are slower, many locations -- such as Santorini, which he calls "a must-see gem" -- are out of reach for those on short holidays. Motor sailers, basically powerboats with sails, tend to be chosen by people who can't decide between the two ways of traveling.

Fortunately, a good yacht broker seeks to match client and boat. "Whether we're contacted by Internet or by phone, we talk a lot with potential clients to get as much information as we can about what they want," says Ed Hamilton, head of yacht brokerage Ed Hamilton & Co. in Maine, which charters yachts in both the Caribbean and the Mediterranean. "Then we can see which boats will fit with their requirements."

There are 2,000 islands out there, so deciding where to go can be quite an involved process. Brokers often help in advance with an itinerary after getting an idea what a client is interested in.

One common route for a seven-day tour goes through the so-called Seven Islands of the Ionian Sea, from flowery Zakinthos to mountainous Corfu with its cliff-faced inlets and the rugged small island of Paxos, with its seaside caves and olive groves. (One piece of advice is to stick to one area -- the Cyclades, say, or the Ionians. Trying to hit islands in different areas makes for too much travel time.) For novice sailors or people interested in a smooth ride, the Ionian Sea is a good choice. Lying between Greece and Italy, it isn't affected by the meltemi, a cold dry wind that hits most Greek waters between June and September and can reach 50 to 60 knots (about 90 to 110 kilometers an hour) -- making sailing a challenge, to say the least.

"The Ionian islands are beautiful and the easiest to sail," says Maurizio Ricchiuto, a longtime sailor from Italy who has visited Greece by yacht. In addition to Zakinthos, Corfu and Paxos, they include Odysseus's legendary homeland, Ithaka.

Some larger brokers, with multiple bases, allow one-way charters -- a course from one base to another. A one-way course downwind offers the opportunity to see more in one trip than a course that must return home into the wind, Mr. Willemsen notes.

Your route will be limited by how much time you have, of course. While the Northern and Eastern Sporades, for example, are less touristy than the Saronic and Argolic gulfs, their greater distance from Athens may make them out of reach.

Sailing from island to island and doing some exploring (by bicycle, for example; many yachts have bikes on board) isn't the only possibility for a yachting vacation. Dia Pappas, a fast-talking Greek-American who has worked at Big Blue Yachting in Athens since the 1980s, says that, for her, visiting six islands in a week by boat is the only way to see Greece, but she notes that "for some people that's not as appealing." One popular choice: four- to five-day turtle searches in the Ionian Sea.

Whatever you do on land, you can try to do on a yacht, too. "We get all sorts of requests," says Mr. Hamilton. "Special foods and delicacies might be flown in from obscure places. Or short helicopter flights." Ms. Pappas says the wildest request she ever had was for a piano to be placed on board a 39-meter yacht. "So I ordered a little white baby-grand to be delivered to the port and loaded," she says, shrugging.

When's the best time to go? If you want to avoid those strong meltemi winds (and this year, the Olympics), cross off July and August. September and October, when the weather has cooled down a bit, are appealing months because much of the most spectacular sea life -- Greek waters are host to striped dolphins, sperm whales and more -- tends to have returned from the north, where they spend their summers.

"September is a wonderful time to tour the Greek islands," says Aris Drivas, an Athens-based yacht broker with 23 years' experience. "The August crowds are gone, the weather's more comfortable, and you just get a lot more sailing done."