"If you've got a little sore and you're out there, get ... in the shower fast with soap to clean that up," she said. "Otherwise, it's horrible."

On sunny days, Hilo Bay looks greenish-gray. After a good rainfall, it's dirt-brown from tons of sediment washed down the Wailuku River and Wailoa Stream. On those days, it is difficult to believe the bay was once a favorite surfing spot of Kamehameha the Great.

Hilo Bay, with its nearly two-mile-long breakwater, is one of the most visible stretches of ocean on the Big Island, but modern-day development and industry have done terrible damage to its waters and marine life.

A breakwater completed in 1929 trapped debris from the Wailuku and Wailoa rivers inside Hilo Bay. Today the trapped silt and turbidity are blamed for the bay's declining coral reef and reduced marine life. Kevin Dayton • The Honolulu Advertiser

Now, county and federal officials are getting ready to develop a computer model to learn whether they can speed the bay's natural healing process. One option that will be tested is a reconfiguration of the 10,000-foot breakwater to allow better water circulation.

Hilo's surfers, divers and fishing enthusiasts like the idea of cleaner water and a healthier bay. Other swimming areas around Hilo are jammed on the weekends, they said, but few people go to the bay to swim. Apart from the canoe clubs that practice and compete there, Hilo Bay's black sand beach is often empty.

Chuck DeCoite

The history of the bay is a study in the destruction of an ocean resource.

Visitors in the early 1870s described the bay as a hub of recreation, with men and boys playing in the surf while men and women dashed around the beach on horseback, according to "Hilo Bay: A Chronological History" by Marion Kelly.

In the late 19th century, the growing sugar industry in East Hawai'i demanded a better and more protected port, and the breakwater was constructed on Blonde Reef to shield ships from rough waters as they entered Hilo Harbor.

The breakwater was completed in 1929, and had the effect of trapping much of the debris from the Wailuku and Wailoa rivers inside the bay. Today the trapped silt and turbidity are blamed for the still-declining coral reef and reduced marine life inside the breakwater.

Hilo's first sewer system was completed in 1906, but the ocean outfall dumped raw sewage inside the breakwater.

A 1952 study by the territorial government estimated 3.5 million gallons of raw sewage were being dumped in the bay each day, with more pollution deposited by Hilo Sugar Co. and ships in the harbor. A 1960 study described the water pollution in the bay as "terrifying," and warned of the possibility of a water-borne epidemic.

The improvements have been gradual.

A new sewage treatment plant was built, and the sewage outfall was moved outside the bay in 1966. That was an enormous improvement, but there is more work to be done, said Walter Dudley Jr., a marine science professor at the University of Hawai'i-Hilo who has studied the bay.

"We have a sewage treatment plant, but much of the community is not tied into it and continues to use cesspools, and that produces a lot of domestic nonpoint source pollution which enters the ocean," he said.

Dudley wants more homeowners to be required to hook up to the county sewer system.

Mauhili said water quality in the bay improved again with the end of sugar processing in the Hilo area in the late 1970s. Closing the mills and plantations dramatically cut down on the amount of bagasse and other debris that used to wash down the Wailuku River, which drains a 250-mile area.

"This whole place here looked so black," she said. "Now, at least you can see some blue spots. Before, it was all black."

Last week the Hawai'i County Council set aside $250,000 to develop the computer model to determine the next steps that should be taken to improve water quality in Hilo Bay. The model will be developed under an agreement with the U.S. Army Corps of Engineers.

Two ideas the project will test are the possibility of dramatically reducing the size of the breakwater, or creating openings in it so that shipping can continue to be sheltered even as water circulates more freely.

The Army Corps has estimated those changes might cost as much as $50 million to $56 million. Where the funding would come from is uncertain.

Mauhili is skeptical, because she says dirt and debris will continue to wash into the bay from the Wailuku and Wailoa rivers, and sometimes from coastal areas north of the bay.

"No matter how much they're going to spend, it's not going to clean up this bay," she said.

However, she also recalled that after the 1946 tsunami ripped out huge pieces of the breakwater, the bay seemed cleaner for years afterward. "The circulation of the rubbish, I guess it went out," she said. "When they sealed it, that's it."

Others worry that tampering with the breakwater could have dangerous, unexpected consequences.

Tony Henriques

Henriques said the breakwater helped shield the town from worse damage in the 1946 and 1960 tsunamis. He said anything that weakens the structure will increase the tsunami threat to Hilo.

With sugar cultivation finished in the area, the bay is gradually getting cleaner on its own, he said.