Emergency work began Monday to remove loose and cracked concrete from the crumbling seawall at the Waikiki Natatorium War Memorial.
Honolulu officials say a recent inspection revealed that portions of the concrete seawall are severely cracked and could fall into the water, injuring swimmers.
"It is a very old facility. It's been around since the early 1900s, so there's no doubt that it is deteriorating and it's just the test of time," said Collins Lam, director of the city's Department of Design and Construction.
City contractors used a forklift to lower a raft into the water outside the facility. Workers then removed loose concrete from the lip of the seawall and lowered it into the raft. The raft then transported the debris to shore where the concrete will be recycled.
The city posted signs around the structure, asking the public to stay away.
The city is spending $80,000 on the project. Contractors are expected to complete the job in about five days.
But rising south swells Monday night and Tuesday could hamper and delay the project.
"Any kind of work on the water is a very difficult task. Being on the water you have waves, you have all kinds of surf that we have to contend with," Lam said.
The 100-meter ocean pool was opened in 1927 as a tribute to servicemen from Hawaii who fought and died in World War I.
The future of the facility has been long debated. The city is working on an Environmental Impact Statement to determine if it is feasible to demolish the structure, restore the beach and possibly move the Natatorium's arch farther insland.
The results of the EIS are expected in about a year.