A FAMILY IS composed of the sun total of its parts, in our case three daughters, a woman and a man. But when one of those parts is 17 years old, a family vacation that is to some a sweet period of communication is to her an infringement on emerging independence.

So when we decide the entire family will go to the beach, despite the uncertain weather, we compromise by bestowing responsibility -- the 17-year-old will drive. We also allow independence -- one night she can visit a girlfriend in a nearby town.

The station wagon is already stuffed when the friend calls to say her own vacation has been canceled, leaving the 17-year-old stuck with the family for the duration.

Our destination is a rented high-rise condominium overlooking the ocean. It is an early spring ocean, chilling, unbeckoning -- but from our window a stunning backdrop. In this still hibernating beach town, most of our vaction is spent together in our pleasant apartment.

Take three teen-agers, a father, a mother, some books for each, pop music for some, jazz and classics for others, TV game shows some wish to watch and congressional budget hearings most don't want to watch, and the stage is set for a typical family stay.

I silently pledge to ignore the blue Nikes and red Izods strewn about, and instead to concentrate on the ocean's magic.

The visit proceeds something like this: After late breakfast together the girls eagerly and energetically walk the beaches. The parents, who are unevenly matched, play tennis. There is much gained: insights from talking together, rest from late rising and early bedtime, weight from endless eating.

Over a card game the kids, called Five Hundred, which to the parents seems to last for hours, the younger teens ask about their lives when they were toddlers, an exercise that disgusts the eldest. All manage, however, to drum up interest when the father, uncharacteristically, remembers what he was like at 16.

"I really wasn't all that popular until I went to college," he offers.

"Really?" asks the eldest with new interest.

The youngest and the middle child never tire of how the parents met. How the father saw the mother regularly on a bus, would open the doors -- those push-out doors -- for her when she got off, thus becoming known to her as the guy who opens the bus doors. How he found a mutual friend to properly introduce them. The whole business sounds simply ancient to the 17-year-old.

We talk of what it means to have brown skin in America today -- the unique challenges -- and the rewards.

At times, the four women withdraw into their femaleness and talk about their lives. I talk of Mama, whom they called Granny, with soft white hair, tough work-worn hands, and love as boundless as the ocean that pounds the shore beneath our orange-curtained window.

We talk of personhood and freedom.We argue about independence and compromise, and I wonder what they really hear me saying. One speaks of how hard it seems to get from their place to my place, and I assure them that when I was her age the distance also looked very great.

When it is night, midnight and quiet, all are asleep. I watch the 17-year-old, the reluctant family vacationer, resting peacefully, her copy of "The Best and the Brightest" flung aside, and I dim her lights. I know that she is unable to understand what it is like to be a mother or a mature woman. I know that to fret over lines of communication within families would to her seem corny.

But something has been communicated despite her resistance -- stability in a chillingly complex and at times unjust, even evil world.

In the long fight towards finding herself and survival, I know this child-woman of our family will need all the stability we frail adults can muster.

And the next day, the drive back to Washington in our stuffed station wagon is much calmer and easier than the trip to the beach.