Romantic Washington-area residents who long to cruise under sail have two good opportunities for adventure from now through next month.

The 200-ton, 126-foot schooner Western Union leaves the Baltimore Inner Harbor every Monday morning for six days of exploration around the Chesapeake Bay. "We may sail up the Wye River to find some crabs, or visit the museum at St. Michaels. It depends on the wind, weather and the whims of the ship's company," says a brochure about shipboard life and "quiet anchorages."

Passengers are permitted to arrive on Sunday evening and bunk aboard for the night. The Western Union is owned and operated by World/Life Explorations, Inc., P.O. Box 226, Solebury, Pa. 18963. For information or reservations, contact the schooner's office at 3440 Carriage Hill Circle T-1, Randallstown, Md. 21133 (phone 301-655-4145).

The windjammer Mystic Whaler, a 100-foot, 100-ton schooner, recently began her 11th season on the bay. She offers "two-day Sneak-Away cruises" midweek and weekends, and has just added one-day cruises from the Annapolis City Dock with passengers going aboard at 9 a.m. and returning at 4:30 p.m. the same day.

For an additional fee, the one-day trip can become a "One-Day Overnight." Sailors arrive the night before, bunk aboard and then cast off for the short day trip when they awaken. For information and reservations, phone toll-free (1-800-243-0720) or write to Mystic Whaler, Mystic, Conn. 06355.