British actress Sinead Cusack, who opens Thursday at the Kennedy Center in the Royal Shakespeare Company's productions of "Much Ado About Nothing" and "Cyrano de Bergerac," periodically travels in connection with her theater performances. But whether she remains close to her London home or goes abroad, Cusack manages to make vacations with her family something special.

When she and her husband, actor Jeremy Irons, are together in England, they "try and get out every weekend" with their 6-year-old son. They have "endless relatives" and thus "endless places to go" for short holidays in England, Ireland or Scotland. When the couple's careers bring them to New York at the same time, they spend weekends with friends on Long Island or at Sag Harbor.

"We have to travel across the Atlantic a lot and the QE2 is a wonderful way to go; there's so much to do and the telephone can't get at you. You're in limbo for five days."

On her vacations the actress enjoys "quiet, isolation, good food and good wine," and her choices reflect her love of the sea. "I need the water . . . it's so peaceful." Some of her favorites:

* Stratford upon Avon Canal, England: "It's one of the most beautiful canals," about 80 miles northwest of London in Warwickshire. "We have an old Victorian punt, a converted sailing vessel 23 feet long."

* County Cork, Ireland: "A little place at Ballycotton Bay is a favorite holiday spot for me and Jeremy and our son. The hotel there is run by three generations of one family, so there are hundreds of kids and your child is taken off your hands from the moment you arrive. It has everything -- swimming pool, tennis court, wonderful food, beaches." She and her husband often go surfboarding.

* Idhra, Greece: "The island has no cars. It's remarkably beautiful and remarkably friendly. I love Greece . . . I love the people, the good food, the whole tenor of the place."

* Chappaquiddick, Mass.: The couple stayed at a friend's home, where there were two boats. "It was blissful. My husband sails, I sail, our child sails with his father."