Sure, it's hard to take synchronized swimming seriously. After all, when a sport's most famous practitioner is a 1940s' and '50s' actress who splashed across the screen in such forgettable flicks as Million Dollar Mermaid and Neptune's Daughter—-well, we're talking image problem. Candy Costie and Tracie Ruiz, who may be the best synchronized swimmers in the world today, don't let detractors bother them. "When someone says, 'All you're doing is water ballet,' " says Costie, "I say, 'Come to the pool and watch us work out.' " Adds Ruiz, "Then they can realize how difficult and athletic it is."

Now that synchronized swimming is going legit at the Los Angeles Olympics (an exhibition sport in 1948, it will be an official event for the first time this summer), it seems destined to leave the Esther Williams era in its wake. One of two disciplines competed in solely by women (the other is rhythmic gymnastics), synchronized swimming doesn't lack for spectator appeal. Indeed, the 34,000 tickets for the two-day competition sold out almost immediately.

The onlookers have a good chance to see the U.S. capture a gold medal. Three-time national champions, Costie and Ruiz blasted the competition out of the pool at the Pan American Games in Venezuela last summer. Their longtime coach, Charlotte Davis, attributes the duo's success to three things: "Both have a feeling for music, they are so strong they can make moves others can't and, most important, they are really smart."

In defense of their sport, Costie and Ruiz point out that they train as rigorously as any gymnast or figure skater. Often rising at 4:30 a.m., the Bothell, Wash, athletes log 35 hours a week in a pool and put in thrice-weekly Nautilus sessions supplemented by biking and running. "I see more of Candy than I do my family," says Tracie. Costie and Ruiz, both 21, have been synchronized swimmers for 10 years. They are rivals as well as partners. "I was used to winning the solo events until I was 15," Costie has said. "Then Tracie started beating me. It was very hard for me at first." Ruiz, who is the more consistent soloist, is the reigning national champion; Costie is right behind. "We compete every day," Ruiz notes. "The intensity has pushed us to the top, but in the duet we pull together."

At the Olympics there will be no solo competition; only the duet will be contested. Divided into two sections, it consists of a series of compulsory figures that count for one-half of the final score. With names like the heron, the albatross and the flamingo, these figures are performed without music and by each duet member separately (the scores are combined).

The second half provides the pizzazz. In their four-minute freestyle program, the two women stroke, slither and twirl in unison, at one point without taking a breath for 53 seconds. Costie and Ruiz will perform to music from Chariots of Fire, Michael Jackson and the German film Das Boot, and will include moves of their own devising. Seven judges grade the competitors on creativity, execution, the amount of territory covered (the more, the better) and their ability to move as one.

In a sport that strives to create mirror images, being sisters or, better yet, twins offers a tremendous edge. (Indeed, some of the duo's stiffest competition has come from Canada's Vilagos twins and Ohio's Josephson sisters.) Though unrelated, Ruiz and Costie, wet, could pass for sisters in their matching rhinestone-studded suits. They are both 5'4" and weigh 118 pounds. (Costie recently shed 22 pounds to reach that number.) Yet out of the water, they are as different as a bubbly blonde (Costie) and a soft-spoken brunette (Ruiz) can be. Ruiz's mother, an executive secretary, divorced her first husband when Tracie was 5. Tracie has since adopted the last name of her stepfather, a machinist. Costie's father is a retired phone company employee and her mother is a bookkeeper. Neither family is affluent, so the athletes rely in part on a community fund sanctioned by their federation to cover training costs.

When the Olympics are over, Costie and Ruiz plan to graduate from the University of Arizona, where they were sophomores on matching athletic scholarships until they dropped out to train in 1982. After that, it's communications for Costie and marketing for Ruiz. Yep, different strokes for different folks. But through the Olympics they will be in perfect synch.