The French are calling it "Underwatergate" and still trying to assess How High the Blame in the July 10 bombing of the ship Rainbow Warrior, but at Greenpeace U.S. headquarters on Connecticut Avenue yesterday it was business as usual: 28 rainbow warriors trying to save mankind from itself.

The people who work on toxic waste were poring over files, the wildlife section was worrying about the environmental destruction of Antarctica. Down another narrow hallway, the national campaign director was cooking up legal strategy for the 12 Greenpeaceniks arrested in Toms River, N.J., in April for plugging a Ciba-Geigy pipeline pouring chemicals into the Atlantic. And last but not least, in a reception room slightly more swank than in the old days, two receptionists were logging the checks and contributions.

"We've gotten hundreds and hundreds of letters expressing sympathy and anger," says Nancy Foote, former crew member on the Rainbow Warrior and now national membership director.

It used to be that the 20 or so fundraisers who go door to door in metropolitan Washington had to explain what Greenpeace was, Foote says. Since the bombing of the organization's flagship in New Zealand and the resulting death of a Greenpeace volunteer -- sabotage since linked to the French secret service -- no one has to be told. "We get people saying, 'Okay, that's it, sign me up."

There have been other changes, too.

"A note of seriousness has crept in," says Stephen McAllister, Greenpeace national campaign director. "When they start killing people, you start looking at packages that come over the door. France made a big mistake. Arguably a lot more people know about Greenpeace now. In a very strange way the bombing has helped the cause."

They were pretty serious anyway. Since its founding in 1971, by a group of Canadian environmentalists, the Greenpeace organization has functioned as a high-visibility environmental SWAT team. They've lashed themselves to whale harpoons, leaped from smokestacks at an Ohio nuclear power plant (with parachute), sprayed baby seals green (to make the pelts unsalable), been arrested and held five days in Siberia and boarded military vessels to prevent offshore dumping of nuclear waste. All of which might sound like hijinks on the high seas until you see the photographs: small groups of people clinging to small ships and rubber rafts in rough gray waters, confronting whale hunters.

They've grown up in 15 years. In addition to oceangoing protests, they now work as nongovernmental observers to international bodies like the United Nations and the International Whaling Commission.

They've been called a "Hippie Navy" and satirized in the comic strip "Bloom County" as extremists who play flutes to whales. And it is hard not to smile when McAllister explains he is off to Mexico because "the turtles are in trouble." But the work is serious, and at salaries that vary from zero to $20,000, no one is in it for the money. The salaried minority, says media director Peter Dykstra, "make enough to stay heavily in debt."

The Rainbow Warrior was the flagship for a fleet that numbers at least a half dozen. It was in New Zealand preparing to lead protest ships into the French nuclear testing area in Mururoa Atoll in French Polynesia when it was bombed in Auckland harbor. Two French secret service agents are awaiting trial in New Zealand on charges of conspiring to blow up the ship and killing a Portuguese-born photographer. Greenpeace has set up a $100,000 fund for the photographer's two children. The heavily damaged Rainbow Warrior has been replaced with a vessel donated by the Association of Maryland Pilots. The new ship, renamed the "Greenpeace," is now on its way to New Zealand.

Greenpeace headquarters is in London and the group has offices in most western European countries, and they're hoping to branch out to the Third World and behind the Iron Curtain. The U.S. office moved from San Francisco to Washington five years ago. The office is small, the style comfortable: posters of whales and ships and presidents, news clippings. Creedence Clearwater Revival playing. But they've acquired a mailing list, and fancy fund-raising techniques like the Greenpeace catalogue of must-haves for the environmentally aware ("Why You Should Buy the Perfect Whale Watcher's Camera"). They say, however, they've remained true to their ideal.

"We're a very different group of people from most environmental groups," says spokesman Dykstra. "Washington politics lends itself to compromise . . . that doesn't necessarily work in nuclear arms. It's not necessarily a victory if you talk someone into dumping 500,000 gallons of nitrobenzene instead of 1 million gallons."

"Most environmental groups first sit down among themselves to work out what they think the government will accept," agrees McAllister. "Whereas we believe in going in and saying, 'No dolphins should be killed, no waste should be dumped.' So we end up being a little out of the mainstream. What you usually argue about in Washington is how quickly things are going to hell, the slope of the destruction. You know, James Watt's 'The world is going to end in the year 2000 so why bother.' National Wildlife Federation would say, 'Let's slow it', and we say, 'Let's stop it'. So that's what gives us that little bit of zeal."

They claim 500,000 supporters in the United States, 1.4 million around the world, and an annual budget of between $12 million and $14 million.

Since it was founded in 1971, Greenpeace's tactics have been controversial among governments, corporations, fishermen and hunters and even some environmental groups. But even in their riskiest undertakings, Greenpeace has never been physically attacked. "I've been arrested by the Soviets in Siberia . . .," says Foote. "But never in that whole time did we ever think we'd be the targets."

They hope the international outrage over the French government's apparent sabotage will discourage any future violence, and they've hired Washington lawyer Lloyd Cutler to sue the French government for damages. Cutler said yesterday that his legal team has not yet decided how much to claim in damages, "But we expect it to be in the millions." His firm is working pro bono, which means they will not bill Greenpeace but can expect some recompense if France is ordered to pay damages.

The sabotage of the Rainbow Warrior appears to have left the corps on Connecticut Avenue unchastened and undeterred. As they sat in the office yesterday, discussing future projects -- such as trying to keep Antarctica from being carved up by multinationals, or worse yet, being used as cold freeze for superpower warheads -- their eyes blazed with the certainty and they had the happy look of people who have found their life's work. Maps are consulted, strategies weighed, anything to halt what they see as the insidious, and accelerating, destruction of water, air and land by nuclear waste, chemicals, development and the threat of nuclear war.

"I consider it a calling," says McAllister, 36, a lanky Vietnam veteran who grew up on a Vermont farm. "Once you've become aware of what's going on, you can't quit. I can't go back to milking cows. This is too urgent.

"I'd like history to show that the dark days were coming and something did happen to turn it around. I feel it's my calling, my job as a human being."