The wait is almost over.

In just five days, visitors to the St. Louis Zoo can enter a 35-foot-long underwater, clear acrylic tunnel and watch sea lions swimming above them.

That's just one of the features of the much anticipated Sea Lion Sound exhibit that opens to the public on Saturday. The 1.5 acre, 10,400-square foot space combines the zoo's popular Sea Lion Basin and Sea Lion Show.

Carla Struckhoff, a St. Louis mother of six who got a sneak peak while visiting the zoo last week, can't wait to see the addition to what she calls the "greatest zoo anywhere."

"We are very excited, and the underground, walk-through exhibit (will be) outstanding," Struckhoff said. "I think it will be different. I think (my children) will probably like the show with the tricks, and I think they will like them swimming over them. I can see my kids in the tunnel saying, 'Wow!'"

Don Greer, a St. Louis Zoo volunteer for seven years, soon will be spending his afternoons fielding questions and directing people to what is being referred to by zoo employees as the "heart of the zoo."

"I think it is going to be a major draw for the zoo," Greer said. "To be able to see underneath them is really pretty awesome, particularly with kids to find out how animals live in the water. And it's much better than having them in a cage."

Construction of the $18 million project started in fall 2010. It opens for zoo members Friday and for the public on Saturday.

The exhibit is equipped with water pools of varying depths with saltwater filtration systems and a shallow beach area for the marine mammals to use for feeding, training and sunbathing.

Mammal curator Steve Bircher, exhibit architects and designers traveled to the Pacific Northwest to get a better feel for the natural environment in an effort to provide the 11 sea lions and one harbor seal with a more accurate habitat. The coastal landscape includes rock outcroppings, land contours, conifers and hand-selected trees from Oregon.

Greer thinks the effort was worth it.

"You get the feeling of being in that area because the foliage and the way it is placed and the buildings, which are different too. It looks like the north(west) coast of the United States," Greer said. "I think those types of exhibits give people a sense of how these animals really live, and I think the sea lion exhibit is going to do that."

Carol Roam, of Lebanon, Mo., checked out the exhibit through construction fence peepholes.

"I remember the dolphin shows when I was a kid, and I would like to see the sea lions. Iit looks like a really pretty facility," Roam said. "I'm just amazed at everything they can do here at the zoo and it still be free."

In addition to the clear acrylic tunnel, there will be an expansive transparent window for further viewing on the deeper end of the water pool.

The Lichtenstein Sea Lion Arena is outfitted for seasonal live shows on the large stage. Trainers will work with the sea lions to do front flipper walks, balancing acts, frisbee throws and hurdle jumps. There is a high diving platform and slide, as well as a rock bridge that reaches into the audience. There are 811 seats for spectators.

Recently installed in the tunnel was a lenticular motion mural consisting of 135 individual 8-inch tiles with ribbed lenses created by world renowned Boston artist Rufus Butler Seder.

"It's sea lions swimming," said Howard Bowen, vice president of Architectural Glass Inc. and Seder's right-hand man. "There are small glass tiles assembled in a mural, about 18 feet long. So as you walk down the tunnel, these sea lions and fish swirl around on the mural and actually move along with you as you walk."

The mural is valued at about $80,000.

"Some people walk or run back and forth, making the pictures 'move,'" Seder said on his website. "While others stop, stare, smile to themselves, and sway from side to side. The people can be as fun to watch as the work itself."

Sea Lion Sound is part of the Living Promise Campaign, which has a goal of $120 million. The campaign has reached $102 million through gifts from individuals, corporations and foundations, said Susan Gallagher, public relations director for the zoo.

"The capital cost for doing something like this comes from private and corporate donations," Gallagher said. "So, they paid for it, not the taxpayers."

Contact reporter Robyn Kirsch at rkirsch@bnd.com or 239-2562.

What happened to the seals?

Sea Lion Sound will be home to 11 California sea lions and one harbor seal.

Originally, the St. Louis Zoo staff anticipated the arrival of four harbor seals from Storybook Gardens, a London, Ontario, theme park. Two of the seals died during transit on June 8. Another became ill and died June 13 during treatment at the Indianapolis Zoo.

The cause of the deaths is still under investigation. The deaths of the three seals will not affect the opening of Sea Lion Sound.

The surviving 18-year-old harbor seal, Peanut, has been under quarantine since June 9 and is doing well.

"We hope to learn the cause of death for these animals, something that remains a mystery since we did everything we possibly could to ensure the safety and comfort of these animals," Dr. Jeffrey P. Bonner, president and CEO of the St. Louis Zoo, said in a statement. "There is always some risk inherent in any animal transport, but our zoo does approximately 200 animal transports annually with no problems, so this has been a very troubling and tragic event for all involved."

At a glance

What: Sea Lion Sound exhibit

When: Opens Friday to zoo members; opens to the public Saturday

Admission: Free to the exhibit, including walking through the 35-foot tunnel and observing the swimming pool and feedings; $4 for the sea lion show; free for children under 2

Best advice: Get sea lion show tickets upon entry to the zoo due to possible high crowd volumes

Sea Lion show times (starting June 30): 11 a.m. and 1:30 and 3 p.m. every day; additional shows at 5 p.m. on Saturdays, Sundays and holidays.

Differences between sea lions and seals

Sea Lion

Family: Otariidae

Characteristics:

Earflaps

Larger, strong, hairless front flippers. Hind flippers allow for rotation toward the ground

Able to walk on land with all four flippers

Uses front flippers to swim underwater using bird-like motion

Smooth, long whiskers

No claws

Longer neck

Doesn't need thick layer of blubber for warmth; comes from southern warm waters

Seal

Family: Phocidae

Characteristics:

Earholes, not earflaps

Smaller, weak, hairy front flippers

Uses front flippers to steer and hind flippers for power when swimming underwater

Able to wiggle and sqirm clumsily on land, not walk

Crimped, short whiskers

Long claws

Shorter neck

Has thick layer of blubber for warmth; comes from northern cold waters

* Both are members of the Superfamily Pinniped, along with walruses.