"We can't hum - our gills are all gummed up," intoned Mary Claire Delaney tragically, exiting stage right and dragging her crepe-paper fins behind her.

Delaney, who in real life is a kindergarten kid, had a small swim-on role in the Capitol Hill Arts Workshop production of "The Lorax," culmination of a four-week children's arts camp held last summer. At various drama camps and workshops scheduled for this summer, kids can whirl like egg-beaters, agitate like washing machines, bump into walls that aren't there, create a language for characters from outer space and act out their dreams.

"We'll be relying on the children's creativity with dreams," says Sally Crowell, director of the Capitol Hill Arts Workshop, which will conduct one four-week arts camp focusing on dreams and one focusing on Middle Eastern myths. "We'll try to get the kids to take off on each other's dreams - to sit down and figure out how a dream can be made into a production that will be enjoyable for other people to watch - without getting into psychodrama, the killing-your-mother sort of thing."

The three-hour-a-day essions will include classes in graphic arts, dance, tumbling, music and drama - all geared toward the production that will be viewed by parents and friends at the end of camp.

Teenagers enrolled in the Archaesus Theater School apprentice program at Duke Ellington High School this summer will perform not only for family and friends, but in shows put on for the public in parks and day-care centers. In the morning sessions of the eight-week course students will attend workshops in mime, dance, improvisation, black theatre, juggling, clowning and stage combat. In the afternoons, they'll put what they've learned into practice in actual productions.

Archaesus also offers a four-week session for nine- to 12-year olds in what director Gary Young calls "non-competitive creative dramatics."

Limited to a dozen kids, the course concentrates on mime, dance, acting, improvisation and makeup. Kids practice mime walks, for example, and go into "the philosophy and reality of imaginary walls," according to Young.

"We might start with a real wall - look at it, feels its texture and temperature, smell it. Then we'd move a few inches away to an imaginary wall. Since they're still kids, their imaginations are still working."

Kids in the Street 70 theater program run by the Montgomery County Recreation Department use their imaginations to create an original play, with the aid of professional playwright.

"Last year the kids in the teen program read a play written by our professional playwright and told him they did't like it because the characters were all cliches," says Jeff Davis, who heads the program. "So we asked them to think about the people they see in the halls at high school, and to make up a character based on that real person. We ended up with a series of character sketches that the playwright helped out together into an orginal play called 'Year-book.' It was videotaped and is used in classrooms by the Montgomery County School system."

This year, kids in the Street 70 program will have a professional composer at their disposal to help them turn their imaginings into a musical. Teens who really want to immerse themselves in theater can attend a five-day resident camp at Hood College, attending workshops from 7:30 in the morning until 11 at night. At the end of the week, the 90 kids at the camp put on a 90-minute show. "That's one minute per kid," says Davis, "But they can pool their time. If one kid wants to sing a solo, he gets one minute.But if four kids want to act out a scene from 'Who's Afraid of Virginia Woolf?' they get four minutes."

For really young thespians - the four- to six-year-old set - the Smithsonian Resident Associates are offering a six-session course called "Miming Machines - Exploring the World of Machines Through Creative Dramatics." The kids look at various machines in the Smithsonian museums and then become parts of machines by improvisation.

Besides learning, by doing, how a hand drill or a washing machine works, what do kids get out theater workshops and drama camps?

"Kids gain a glitzy point of view of what they can personally do," says Gary Young of Archaesus. "They gain self-confidence, and they acquire another tool for self-expression, for communicating with others."

Vivian Hill, who will help conduct a "Character-Building" program for children six and up at the Adventure Theater in Glen Echo Park in summer, has a different answer.

"Drama courses should provide an opening, another way to look at the world . . . Perhaps a tree isn't always a tree; perhaps sometimes it's an umbrella." CAPTION: Picture, ANDREA McARDLE AND REID SHELTON AS DADDY WARBUCKS IN "ANNIE." By Martha Swope.