Some Ewa Beach residents and an elected official threw their support Sunday behind plans to convert an undeveloped marina into a public recreational lagoon aimed at families.

"I see a whole new generation of people growing up with the largest enclosed water feature in our community," said Rep. Kymberly Marcos Pine (R, Ewa Beach-Iroquois Point). "This will help bring a whole new health culture in Ewa Beach."

Pine trains for triathlons at Ala Moana Beach Park but would prefer to do her swimming workouts in the enclosed, 54-acre brackish-water lagoon — bounded by White Plains Beach and Oneula Beach Park — that was carved out of coral and originally planed as a marina that never materialized.

"I see triathletes wanting to come out here for their races," Pine said. "And there will be lots of families, too. Ewa Beach families are very large and close-knit and like to do everything together. With this lagoon we’ll never leave our community."

The enclosed coral lagoon is a half-mile across and 1,000 feet wide and sits about 19 to 20 feet deep, depending on the tide, said Sharene Saito Tam, vice president of Haseko Development Inc.

Haseko had planned to include the marina as the focal point of its planned $1.4 billion waterfront community, the 1,100-acre Ocean Pointe and Hoakalei Resort in Ewa Beach.

Motorized boats and watercraft would be banned, but there would be ramps for nonmotorized kayaks and stand-up paddleboards.

Ewa Beach residents who want to enjoy tranquil waters now have to go through a security gate at the Ko Olina Resort in Kapolei and have to be in place by 7 a.m. on the weekends — or by 5:30 a.m. on a holiday — to get a spot at one of Ko Olina’s lagoons, Pine said.

The Ewa Beach lagoon would be open to the public and would include an enclosed swimming area for children and families that would be no deeper than 6 feet, Tam said.

Sea water would be pumped into the swimming area throughout the day, Tam said. The swimming area could be developed by the end of 2015, Tam said.

It would be the perfect site for Ewa Beach resident Tony Becker to enjoy his grandchildren.

"This is a great opportunity for us as a family," Becker said. "My grandkids want to hang out in Ewa Beach."

Haseko has not estimated how many people would use the lagoon and swimming area, Tam said.

There would be bathrooms as well as parking on the mauka, Ewa and Diamond Head ends of the lagoon, which would include a bridge to let people walk across the lagoon to get to other areas.

There also would be an unknown number of businesses catering to families, Tam said.

Kaui Serrao, co-founder of the Puuloa Outrigger Canoe Club, was raised in Ewa Beach and is eager to see the lagoon open.

"It’s big changes but it’s good for our community."