CHARTERS: There are dozens of companies that charter boats in the Virgin Islands. Some maintain their own fleets, others serve as booking agents for smaller companies. Some also charter powerboats.

Most of the fleets available for bare-boat chartering in the area are located on St. Thomas in the U.S. Virgins and Tortola in the British Virgins. Rates are substantially cheaper in the off-season (generally mid-summer until December), and some companies offer discounts for charters that run longer than one week. But beware of significantly lower rates: They may reflect a smaller support staff and perhaps a lower level of maintenance on the vessels themselves. It's also important to note that the insurance coverage of some companies may prohibit charterers from attempting the open-water passages to St. Croix in the U.S. Virgins or Anegada in the British Virgins.

Most of the charter companies will arrange for at least some of your provisioning, and it's a good idea to allow them to do so, since provisions can be hard and/or expensive to come by. You can opt for having all your meals provided by the company; just breakfast, lunch and snacks; or breakfast, lunch and half your dinners. In addition, arrangements can be made for custom or gourmet provisioning through companies such as the Ample Hamper, Box 697, Tortola, B.V.I., which offers partial provisioning for $11.75 per person per day.

Among the companies that offer charters in the Virgin Islands -- including a sampling of their rates, the smallest and biggest sailboats in their fleets and their highest and lowest seasonal rates (some firms have as many as four or five "seasons") -- are:

The Moorings Ltd., Suite 402, 1305 U.S. 19 South, Clearwater, Fla. 33546, (800) 535-7289. The fleet is located in Road Town, Tortola, B.V.I. Rates range from $1,162-$2,380 a week for a 37-foot vessel that sleeps four to $2,394-$3,997 for a 51-foot vessel that sleeps eight. Rates include transfers from the airport on Beef Island. Full provisioning costs $16 per person per day; a skipper can be hired for $76 a day, including his food.

C.S.Y. (BVI) Ltd., c/o C.S.Y. Inc., P.O. Box 491, Tenafly, N.J. 07670, (800) 631-1593. The fleet is located in Road Town. Rates range from $1,225-$2,443 a week for a 42-foot vessel that sleeps six to $1,799-$3,395 for a 50-foot vessel that sleeps eight. Provisioning is $15-$16 per person per day; a skipper can be hired for $70 a day.

Fun in the Sun Yacht Charters, 320 North Federal Highway, Dania, Fla. 33004, (800) 327-0485. This company represents several fleets in various locations; its boats range from a 30-foot vessel that sleeps four and costs $1,190-$1,510 a week to a 51-foot vessel that sleeps eight for $2,575-$3,850. Provisioning is $14 to $17 per person per day; a skipper can be hired for $60 to $70 a day.

Caribbean Yacht Charters, P.O. Box 583, Marblehead, Mass. 01945, (800) 225-2520. The fleet is located at Compass Point, St. Thomas. Rates range from $1,195-$1,695 a week for a 32-foot vessel that sleeps four to $2,395-$3,795 for a 52-foot vessel that sleeps eight. Provisioning is $13.95 to $17.95 per person per day; a skipper can be hired for $65 a day.

North-East-Wind Yacht Charter, P.O. Box 4220, 326 First St., Annapolis, Md. 21403, (800) 638-5139; in Maryland, (301) 267-6333. The fleet is based at Crown Bay, St. Thomas. Rates range from $760-$1,275 a week for a 30-foot vessel that sleeps four to $1,780-$2,980 for a 46-foot vessel that sleeps six or seven. Provisioning is approximately $16 per person per day; a skipper can be hired for $80 a day. INFORMATION: Perhaps the best sources of information about bare-boat chartering in the Virgin Islands are boating and sailing magazines. Cruising World magazine, for instance, publishes an annual worldwide chartering guide; the most recent one appeared in its July 1987 issue.

In addition, two excellent guides are:

"The Cruising Guide to the Virgin Islands," available from Cruising Guide Publications Inc., P.O. Box 13131 Station 9, Clearwater, Fla. 34621, (813) 796-2469. The cost is $13.95 plus $2 postage and handling.

"Yachtsman's Guide to the Virgin Islands and Puerto Rico," available from Tropic Isle Publishers Inc., P.O. Box 610935, North Miami, Fla. 33161, (305) 893-4277. The cost is $12.95.

For more information, contact the U.S. Virgin Islands tourist office at 1667 K St. NW, Suite 207, 293-3707, or the British Virgin Islands Tourist Board, 370 Lexington Ave., New York, N.Y. 10017, (800) 835-8530.