Not long ago, flood waters washed over the green banks of the Russian River near here, caught up a few ill-fated cows and carried them out to sea. Three days later, the carcasses were found 300 miles north on the beaches of Oregon.

The ocean, with its unpredictable currents, does things like that off this rugged, scenic and productive coastline north of San Francisco.

The fisherman, tough men like George Setzer with wind-etched faces and gnarled hands, watch those tricks of nature. They watch because the know the fish follow the currents, the albacore invariably trailing just behind surf-sailer jellyfish, the prized king salmon ducking the warm currents for the cold.

They also watch because they figure oil would follow the same unpredictable currents, sweeping up and down this coastline.

They are thinking about oil because Interior Secretary James G. Watts wants to open up four tracts of ocean floor to leasing for oil drilling off the coast of Northern California. It is the second stage -- the first also took place in California -- of Watt's plan to offer a billion acres of offshore lands to the oil companies in the next five years.

Watt, who prides himself on quick and provocative decisions and who says he is fed up with government's "paralysis by analysis," decided just two weeks after he took office to buck a Carter administration decision to avoid this coast. He could not have picked a more troublesome place to get his new policy under way.

All the currents seem to be running against him out here in President Reagan's home state, none more strongly than the political tides.

Watt's decision has done what some might have thought impossible -- made political bedfellows out of Democratic Gov. Edmund G. (Jerry) Brown Jr. and Republican Sen. S. I. Hayakawa, allies out of such philosophical opposites as Democratic Rep. Phil Burton, a San Franciso environmentalist, and Rep. Don Clausen, a north coast Reaganite who tilts toward resource development.

In fact, the controversy has so turned California politics on its ear that it may prove to be Watt's first major undoing at Interior. The Interior Department's top spokesman, Doug Baldwin, confirmed last week that the final decision has been removed from Watt's office and taken to the White House.

Out here, where the surf sends spray hundreds of feet high after pounding into coastal rocks, where "sleeper waves" have been known to appear out of nowhere and sweep whole families off isolated beaches, the fact that a California president has taken the decision away from his Cabinet subordinate surprises almost no one.

Setzer figures he understands the politics of it all just about as well as he understands where to drop his trolling hooks into those Pacific currents. He nodded in understanding when an Oregon congressman, Democrat Les AuCoin, pushed an amendment through the House Interior Committee to block the oil leases.

No oil drilling is planned off Oregon, Setzer acknowledged, but that Oregon politician knew darn well where those Russian River cows beached.

Setzer wears a "fishermen's power" windbreaker -- a jacket emblazoned with a clenched fist closed over an upraised fishing gaff. It is ever got down to hard-ball tactics, the salmon troller figures his buddies might throw a ring of fishing boats around one of those offshore drilling platforms, the same way they surrounded a Navy destroyer after an oil spill in San Francisco Bay a few years ago.

But he doesn't think it will come to that, not with the man the fishermen supported, Ronald Reagan, in the White House. And not with the decision sitting there now.

And especially not with California's Republican state chairman, Tirso del Junco, warning the president that Watt's plan could prevent the GOP from regaining the governorship, cost Hayakawa's Senate seat and control of the state legislature in next year's election.

Or with another California Republican professional, Bill Roberts, who ran Reagan's first gubernatorial campaign, firing off a six-page memo to the White House saying Watt was formenting an outright political disaster that could cost the party a handful of congressional seats as well as the governorship.

Setzer knows that kind of stuff carries more clout than the dead cows, or the two oil-soaked sea birds a local environmentalist dropped on the witness table at an Interior Department field hearing out here two years ago or even all the scare stories about oil spills killing off his salmon.

Earlier this year. when Watt first made his announcement, folks got pretty excited because they though they had their battle won last year with President Carter and his interior secretary, Cecil D. Andrus. Just weeks before the 1980 election, Andrus nixed drilling in the four tracts that stretch from Eureka near the Oregan border to the edge of marine sanctuaries off San Francisco.

The U.S. Geological Survey has estimated that the Northern California tracts have about 11 or 12 days' national supply of oil. Andrus concluded -- Setzer guesses the election had something to do with the conclusion -- that less than two weeks worth of oil wasn't worth the risk to the salmon, the crab and the spectacular isolated beaches reaching north and south from here.

Watt and the oil companies argue that the surveys are notoriously inaccurate, that until they start tapping the beds there is not way of knowing how much oil lies off California's shores. "There could be a new Prudhoe Bay out there and we won't know until we run a drill down," says Watt's man, Baldwin.

The thought of a new, Alaska-type Prudhoe Bay off scenic Bodega Head or edging up to the Farallon Islands game refuge off San Francisco is not exactly reassuring to the locals.

Richard Charter, a lobbyist who represents bipartisan county supervisors in 11 coastal counties, all of which oppose the leasing, says the first reaction to Watt's lightning-stroke reversal of Andrus' decision was a "feeling we had been stabbed in the back."

"No one really thought that an administration that came out of California would do that," says Charter, whose home looks out over the surf at Bodega Head toward one of the tracts. "It didn't really compute."

Now, Charter just smiles as he remembers his first reaction. With the issue sitting in the White House, he figures he was right the first time and that it didn't compute.

Andrus, struggling with his decision last year, visited Northern California several times. Charter recalls that the secretary came out once incognito, like the king in peasant's clothing, wandered the coastline and talked to fishermen and townsfolk until he concluded that the leasing wouldn't wash politically.

The Californians have invited Watt to come out, too. But Watt declined.

Charter thinks Watt, so eager to avoid "paralysis by analysis," trapped himself into making a quick decision that was bound to have a different kind of symbolism -- "a symbolic statement that state's rights depended on which side you were on." That had a special bite producing all that negative political spinoff, Charter says, when Watt wrote off the state of California's opposition as "narrow and provincial."

Watt says he was required by law, which establishes a strict schedule for offshore leasing, to give that quick go-ahead in his first weeks in office or forget the coast of Northern California forever.

Charter, Setzer and most of the rest of the coastal residents out here are betting now that Watt's second option is looking better and better to him.