As her ancestors have done in these waters for 600 years, Queen Elizabeth sailed slowly past her navy at Spithead today to the full-throated roars of 30,000 sailors.

This Silver Jubilee review turned out four long lines, stretching more than seven miles, of sleek gray frigates and cruisers, menacing coal-black submarines and a flotilla of specialist craft - all riding at anchor in the cold green sea.

As impressive as the spectacle was, it is clear that Britannia no longer rules the waves. In February, the navy was reduced to renting some commercial ferries for an amphibious exercise in Norway.

Nevertheless, those endless ray lines of taut, slick ships moved one commander aboard the press vessel to exclaim, almost to himself, "A brave show, a brave show."

Monarchs and their fleets have been meeting at spithead, the channel between Portsmouth on the southern coast and the Isle of Wight, since 1346, when Edward III reviewed 1,000 war ships before setting off to invade France. On the eve of Agincourt, in 1415, Henry V followed suit.

The Queen herself came here in 1953, after her coronation, to inspect the fleet. It contained three times the 150 warships that the royal navy now boasts.

But if her navy was shrunk in size - she saw 99 of her warships today - it has grown enormously in firepower. Authorities say a contemporary frigate - much the same as a U.S. destroyer - can with its missiles outgun a prewar cruiser.

Moreover, the royal navy's most destructive weapons were not at Spithead. They are the four submarines equipped with Polaris intercontinental ballistic missiles that can destroy cities 2,500 miles away. This British deterrent was at sea on war stations, in the Arctic, Mediterranean or Atlantic.

The deck rails and hulls of Her Majesty's Ships were lined today with white-capped men who stood stiffly at attention for two hours under a cold and leaden sky.

Their only relief came when the Queen's vessel approached. Then to an officer's cry of "Hip, Hip" they waved their hats clockwise in the air - a maneuver carefully rehearsed yesterday - and shouted back three times, "Hurray, Hurray, Hurray."

The Queen took their salute from the rear deck of her royal yacht, Britannia, a sturdy vessel built for service rather than style. The only color on its black hull and white superstructure was supplied by three royal flags waving from the masts.

Small private craft, multicolored sailboats and cabin cruisers festooned in red-white-and-blue bunting darted in and out behind the long gray lines of warships to see and become part of the spectacle.

For most in the fleet, the Queen was a dimly perceived figure in white with a green hat, waving a gay acknowledgment of each salute. Beside her the sailors could probably make out Prince Philip and perhaps Prince Charles. He will likely stage a similar review when he is crowned. The Queen's party also included Prince Edward, Princess Anne and her husband Capt. Mark Phillips, and Earl Mountbatten, an admiral of the fleet as well as member of the family.

Prime Minister James Callaghan and his wife, Audrey, were also on the royal yacht but not overly visible. For one thing, this was the Queen's day. For another, Callaghan's Labor government has curbed the navy and other military budgets. So he was not the most popular man afloat today.

The Queen's navy no longer commands the trade routes from Singapore to Spithead. Its more modest role is to protect the eastern Atlantic and hold the English Channel ports - until reinforcements arrive from the U.S. Navy.

The United States was one of 12 allies or Commonwealth nations invited to the Queen's sea party, and it made only a modest showing. The Billfish, a nuclear-powered attack submarine, took its place with the dark hulls of the British subs. The California, a nuclear-powered guided-missile cruiser, and her men stood in the middle of the line. Their band broke out triumphantly as the Queen rode past.

More recently, the British government assigned another mission to the navy, to guard the oil rigs bringing up black gold for Britain in the North Sea. But serious critics question whether much of the fleet, apart from the submarines, make any sense, in the modern world of nuclear missiles. Th argument goes that no major power could attack the shipping of another and expect that the engagement would continue with conventional naval weapons only.

The biggest warship on display here, the aircraft carrier Ark Roayl, is to be put in mothballs next year. Britain then will have no more carriers for fixed-wing aircraft.

Appropriately, the largest of the 170 vessels, civilian and military, was not a warship but the British Petroleum supertanker, British Respect. It can carry more than 1.9 million barrels of oil.

Thanks to North Sea crude oil, Britain has some prospect of regaining a portion of its lost sense of power. Saved from buying oil abroad for perhaps 15 years, Britain need no longer worry about a depreciating pound and can adopt measures to shorten its welfare lines. Whether this will save the navy - once first in the world and now a distant third at best - from further cuts is a question, however.

The review was supposed to end with 44 all-weather fighter planes and strike attackers streaking overhead, forming E II R and an anchor. But the weather defeated them. The clouds hung too heavy.