Crown Center on Wednesday announced a $15 million aquarium that will open in spring 2012. Sea Life Kansas City at Crown Center will occupy the entire 45,000-square-foot first floor and about half of the second floor of Halls department store. Halls will shift some departments to other spaces in Crown Center.

The aquarium will include more than 30 displays — from shrimp and starfish to seahorses, sharks and rays — along with a huge tropical ocean tank with a walk-through underwater tunnel. A regional element will take visitors on a two-to-three-hour journey from “the fresh waters of the Missouri River, into the mighty Mississippi River, then out into the warm blue coral-strewn waters of the Caribbean Sea, ending in the deep, dark abyss of the Atlantic Ocean.”

While construction is expected to begin in May, the final design, including the total number of gallons of water, has not yet been completed. Admission prices also were not disclosed.

Bill Lucas, president of Crown Center Redevelopment Corp., a subsidiary of Hallmark Cards, said the Sea Life aquarium will complement the family-oriented attractions at Crown Center and add to its regional draw along with the nearby attractions of Union Station and the National World War I Museum.

“This is one of the most exciting announcements in our history,” Lucas said.

Merlin Entertainments Group, based in the United Kingdom, will develop the aquarium. The company, a major player in the family entertainment business, has developed nine other attractions in the U.S., including the Legoland California theme park and water park.

It also has Sea Life aquariums in Carlsbad, Calif., and Phoenix. An aquarium at the Mall of America in Minneapolis is being re-branded as a Sea Life and will reopen in a few weeks, and a Sea Life and Legoland Discovery Center will open in the Dallas-Fort Worth area this spring.

Merlin and Crown Center Redevelopment will share the construction costs and will not seek tax incentives. The aquarium will have about 50 employees during peak summer and holiday seasons.

“Kansas City is a great regional destination and we know Crown Center is a place that’s always going to be here, in 20 years, 30 years, and it won’t become glitzy,” said Steve Shears, site search and acquisitions director for Merlin.

In recent years, developers have pitched Union Station, the riverfront and a location near the Sprint Center as sites for a major aquarium attraction downtown. Now it appears the area could soon have not one but two aquariums opening at about the same time.

Across the state line in northeast Johnson County, an aquarium is being planned as a major attraction of the proposed Mission Gateway office and retail project in Mission.

Cameron Group, a Syracuse, N.Y., developer of Mission Gateway, is proceeding with plans for a much larger saltwater aquarium — 2.5 million gallons and around 90,000 square feet. A single 2-million-gallon tank is planned to take up the first floor of the proposed three-story freestanding building. The Mission attraction will be operated by U.S. Aquarium Team of Dallas.

Erik Pedersen, U.S. Aquarium’s chief executive officer, said his attraction might appeal to a wider age group and be more “museum quality” than the Crown Center aquarium. It is projected to cost $35 million to $40 million. Construction could start by this summer with an opening planned for spring or summer 2012. Cameron won state authorization for $63.2 million in STAR bond financing for the Mission Gateway.

Shears, of Merlin Entertainments, said he looked at several area sites before selecting Crown Center. He said the development, which includes the headquarters of Hallmark Cards Inc., had the infrastructure in place with two major hotels, retail, restaurants and other attractions like Kaleidoscope, the Coterie Theatre and the American Heartland Theatre.

“A major investment like this, central location, no incentives, what’s not to like?” said Kansas City Mayor Mark Funkhouser.

As for Halls, the men’s department will relocate to space on the third level of the Crown Center Shops. The Hallmark Cards product department within Halls will be consolidated into the Hallmark store on the second level of the shops, while the home decor and kitchenware departments will be relocated on Halls’ second floor.

The department store’s third level will remain unchanged.

Crown Center Shops tenants were pleased by the news.