Several former top U.S. Navy admirals are sailing into the spreading nuclear arms debate--but in many different directions.

In an appearance at the National Press Club, the former commander of U.S. military forces in the Pacific, retired Adm. Noel Gayler, told his audience last Thursday that nuclear weapons "have no military usefulness."

Gayler said he is convinced that the Soviets are ready for a deal on nuclear arms and suggested that the two superpowers junk thousands of atomic weapons and freeze production of new ones. The United States, he added, should renounce the policy of using atomic weapons first, if necessary.

Earlier this month, retired Adm. Bobby R. Inman, who resigned in June as deputy director of the Central Intelligence Agency, joined the board of directors of the Arms Control Association, a nonpartisan organization that advocates arms control as an element of national security.

Although Inman believes in arms control as the only way to limit Soviet nuclear power, he does not advocate a weapons freeze and views as impractical notions such as Gayler's that huge reductions can be made or that the Soviets are likely to accept them.

In Northern Virginia, the former chief of naval operations, Adm. Elmo Zumwalt, and his former vice chief, Adm. Worth Bagley, frequently write about arms control in a column distributed by the Los Angeles Times to a few dozen other papers. Zumwalt, who retired in 1974, said that while Gayler is "an old friend, I don't agree with his point of view."

"The United States is distinctly inferior" to the Soviets in long-range strategic nuclear arms, Zumwalt said. Previous strategic arms limitation agreements on such weapons were bad, he said, because they froze that inferiority. President Reagan's strategy of an arms buildup in order to negotiate a better deal is the correct course, he believes.

From his retirement home in Arizona, former Adm. Stansfield Turner, who served as CIA director during the Carter administration, also weighs in with articles in major newspapers.

He opposes going ahead with the new strategic weapons such as the MX ballistic missile and the B1 bomber, but he also cautions against restrictions on new jet-powered cruise missiles. He believes they are essential for nuclear and non-nuclear defense because their relatively slow speed makes them less threatening as a first-strike weapon and thus less destabilizing in a crisis.

In Washington, two other former flag officers, rear admirals Gene R. LaRocque and Eugene J. Carroll Jr., run the Center for Defense Information. They publish a monthly newsletter that supports arms control, frequently challenges Pentagon assessments of the military balance and is widely used as an alternative source of information.

Although other voices among the retired military are also being heard, the Navy, for some reason, seems to be supplying most of the participants. And Gayler may turn out to be the most controversial among them.

Gayler, who retired in 1976, has become increasingly involved in the arms control debate as a spokesman for the American Committee on East-West Accord, which advocates improved U.S.-Soviet relations. The committee includes many prominent former officials such as George F. Kennan and W. Averell Harriman, former ambassadors to the Soviet Union, and former secretary of defense Robert S. McNamara.

Some senior officers, active and retired, and some civilian arms control specialists feel the outspoken Gayler has gone too far in stating his case.

One reason Inman was approached to join the Arms Control Association, informed sources said, is to add some balance to Gayler. While Inman will not comment on this, he said he will probably play the role of the conservative in the organization "to make sure they look at the problems as well as the hopes" for arms control.

Coincidentally, Gayler and Inman are former directors of the National Security Agency, the government's electronic-eavesdropping arm and the most secret of the U.S. intelligence agencies.

Both therefore have had access to some of this country's most sensitive information and are potentially important and respected public voices in the complicated debate over nuclear weapons and the prospect of agreements with Moscow to control them.

During his press club appearance, Gayler argued that nuclear weapons are basically genocidal, cannot be used effectively at sea or on land without extraordinary devastation and that each superpower needs only a few hundred of such basically invulnerable weapons to deter attack.

Civil defense against atomic warfare, he said, "is a turkey, a wasted effort." Although the Soviets have a distorted view of what they need for defense, Gayler said there are historical reasons for this and that there is "no evidence that the Soviets are thinking of attacking the United States because they believe our guard is down."

He said the Soviets are ready to reach agreements and urged the United States to assess how much risk there is in dealing with Moscow.

In his view, the worst that could happen--and he does not think it will--is that "we might sign an unequal treaty." But there are so many atomic weapons already that such a risk is minuscule compared to the broader risk of "all of us getting our heads blown off."

"It is no consolation," Gayler added, "that they the Soviets are at as much risk as we are" when it comes to mutual destruction.

After 35 years in the military, including service as a top field commander, Gayler was questioned from the floor about how he came to such views. Another questioner asked whether he also supported the views of the anti-nuclear Greens movement in West Germany and such American dissidents as Daniel Ellsberg and the Berrigan brothers.

Gayler shot back that the Greens are "a bunch of nuts" but that "to be anti-nuclear is not to be anti-military or to be anti-American."

As to how he came to his views, Gayler said he had been in Hiroshima shortly after it was destroyed by an atomic bomb and had also been involved in test explosions in the Pacific after World War II.

"Nothing you can read or see in motion pictures prepares you for that," he said. One problem, he added, "is that so few policy makers these days have seen these things . . . . They haven't any real idea of what it is they are talking about."

Gayler also served on the Pentagon's joint strategic targeting staff and so, he concluded, "I have had a lot of experience with nuclear weapons, and the more you know about them, the less you like them and the less utility you think they have."