In-like-a-lion March winds scoured hundreds of boats sitting on blocks at Herrington Harbour, their hulls awaiting spring cleaning.

"By the end of a year or two of sailing the Chesapeake, they're often fouled with stuck-on algae, barnacles and other marine animals," said Hamilton Chaney, co-owner of the marina. "That increases drag through the water, and they sail a lot slower."

Hull fouling is a problem for boats ranging from dinghies to oceangoing ships. Even a little can drive up fuel consumption by as much as 50 percent, said Kathy Metcalf, director of maritime affairs for the Washington, D.C.-based Chamber of Shipping of America. And then there's lost time and revenue while a ship is dry-docked so the fouling can be removed. "Ideally, we'd like to see a ship's hull as clean as a whistle," Metcalf said.

But keeping a hull clean as a whistle may also clean out the surrounding marine environment, because of antifouling paints. Those paints keep marine life off a hull for one to five years by slowly releasing biocides that kill the organisms that grow on almost any underwater surface.

These additives, the best-known of which is tributyltin, or TBT, function as pesticides, warding off animals and plants that try to attach to surfaces coated with them. But scientists have found that as these compounds leach out of the paint base, they are absorbed by the surrounding seawater and eventually by bottom sediments, where they kill seaweed, mollusks and other life-forms.

TBT may be the most toxic substance ever deliberately introduced into the marine environment, many scientists say, and the International Maritime Organization has banned it as an antifouling paint additive. Although the treaty governing this ban has yet to take effect, TBT is, for all intents and purposes, "a thing of the past," said organic chemist James Readman of the Plymouth Marine Laboratory in Plymouth, England.

"Our worries now, though," Readman said, "are what's in use instead of TBT. In the end, the currently available replacement antifouling paint additives may be just as toxic."

Richard Owen, a marine biologist at the Bermuda Biological Station for Research Inc., agreed. "It looks like we're heading down this path again with additive compounds that have replaced TBT, like Irgarol 1051."

Owen recently published studies of Irgarol's effects on coral reefs that showed two things: First, Irgarol kills zooxanthellae, the sensitive algae that keep corals alive by providing them with nutrition from photosynthesis; and second, there are high concentrations of Irgarol in waters surrounding the Florida Keys, Bermuda and St. Croix, where coral reefs are located.

Naomasa Kobayashi of Doshisha University in Kyoto, Japan, looked at the effects of Irgarol and other alternative antifouling paint compounds, such as Sea-Nine 211. Kobayashi's results also showed that Irgarol is toxic to marine algae, and that Sea-Nine 211 can interfere with the early development of sea urchins.

As far as the U.S. Environmental Protection Agency is concerned, the jury is still out on these substances, said Dennis Edwards of the EPA's Office of Pesticide Programs. Irgarol and Sea-Nine, Edwards said, "are registered for use in this country on a time-limited basis only. We're performing a comprehensive risk assessment on Irgarol, and hope to have a final determination about it in late spring to early summer of this year." He noted that several countries -- Sweden, Denmark and England, for example -- have limited the use of Irgarol.

At Ciba Specialty Chemicals Inc., which makes Irgarol, Dick Balcomb, director of the Toxicology and Environmental Assessments Division in Tarrytown, N.Y., said, "Our studies of corals in Florida don't show them as having been exposed to Irgarol. If they haven't been exposed to it, Irgarol can't have affected these corals. We have no information that would indicate that there's a problem with Irgarol."

In studies Ciba has supported, however, Irgarol was found in Florida waters in which corals live, according to researcher Piero Gardinali of Florida International University. Studies Gardinali undertook last year found Irgarol in Key Largo Harbor, at Looe Key and at Ramrod Key, he said. Concentrations of Irgarol in Key Largo Harbor have been found to be in the range considered harmful for near-shore coral species.

There's a major loophole in EPA regulations, Owen said. "Corals are keystone species under a lot of pressure globally, yet EPA doesn't require data on adverse effects on coral reefs."

Edwards said his agency "in fact [doesn't] require that every plant and animal in an area be looked at; we require that representative plants and animals be studied. That being said, however, if a company has knowledge that a product is causing an adverse effect, it is responsible for letting EPA know."

Some companies are already trying to move away from biocidal antifouling paints. "We're at an interim time between TBT and the products that may come after the alternatives we have now," said Andy Jacobsen, a scientist in the Pennsylvania office of Rohm and Haas, which manufactures Sea-Nine 211. But that interim, he said, may be a decade.

At least one non-biocidal antifouling paint is commercially available now: SigmaGlide LSE, made by Sigma Coatings Inc. It produces a slick surface to which algae and mollusks can't adhere, but it works only on high-speed vessels, because it requires fast water motion to keep hulls unfouled.

Scientists are looking at new antifouling strategies based on the natural attributes of plants and animals, some of which have to keep other plants and animals from settling on them. Polymer chemist Karen Wooley of Washington University in St. Louis has found that the sleek skin of dolphins is, on a microscopic level, rippled rather than smooth, providing a clue to how dolphins keep their bodies free of unwanted hitchhikers. And biologists in France and England say that extracts from various marine algae demonstrate antifouling activity comparable to that of TBT.

One innovative potential antifoulant may be hidden in a plant called guayule, the subject of research by polymer chemist Shelby Thames, president of the University of Southern Mississippi. The compound partheniol, taken from the plant, has prevented fouling on wood and especially metal, but it is rare, and it needs more study -- which would require an investment Thames doesn't foresee.

"We need to be doing this work now, so we have something to offer when current antifoulants are no longer viable," he said.