VENICE -- The tranquil charms of Venice's romantic canals have been spoiled by a noisy onslaught of security measures that have outraged many of the city's 200 gondoliers.

The gondoliers have been banished from their favorite moorings beside St. Mark's Square to the back canals as part of a security plan that has forced Venetians to take long detours. Even the ornate water hearses have been banned from the main canal routes, prompting a headline in the newspaper Il Messaggero: "Please Don't Die During the Summit."

The gondoliers contend that the three-day summit is costing them $150,000 in tourist income and have demanded compensation from the government. So far their appeals have gone unanswered, even though they were paid for income lost during the 1980 summit.

Security procedures are believed to be much stricter than in 1980, when president Jimmy Carter took an early morning jog along the Grand Canal in the company of a few bodyguards.

An army of 8,000 Italian security police has been deployed, with 5,000 assigned to protect President Reagan. The force includes a detachment of frogmen and a paramilitary unit usually assigned to detect smugglers.

VENICE HAS long been known as La Serenissima, which means "the most serene." But the Venetian calm has been disturbed by the constant whir of military helicopters overhead. Venetians also complain that their favorite television and radio programs suffer interference from electronic monitoring gear on a U.S. Navy ship moored in the Grand Canal.

Italian police protecting Reagan have given U.S. Secret Service agents the jitters by pointing their weapons in the direction of the president. Some journalists said that weapons also appear to have been aimed toward them on one occasion.

White House reporters would not appear to pose much of a threat. They have been isolated on a separate island, the Lido, where security is so strict that the manager of the hotel was denied entrance because he lacked a summit pass.

WHEN PRESIDENT Reagan arrived at the Hotel Cipriani this morning for a meeting with Italian Prime Minister Amintore Fanfani, he traveled in an enclosed 30-foot launch, known to the Navy as an admiral's barge. It was accompanied by another launch, two Navy landing craft, eight inflatable dinghies manned by frogmen and numerous police craft.

The president was asked why he would be going in a side entrance Tuesday instead of participating in the formal opening ceremony outside the Cipriani with leaders of other summit nations. Reagan said he did not know.

"I just wait until somebody points me in the direction I'm supposed to go and I don't ask any questions about it," he said.

Administration sources said the Italians expected Reagan to go in the front entrance to the Cipriani, which is on the secluded island of Giudecca. But they said the Secret Service had insisted that the president be taken in by boat through a canopied side entrance and that British Prime Minister Margaret Thatcher had agreed to accompany him.

U.S. TELEVISION network celebrities attracted more attention than some summit leaders. Hundreds of Venetians and tourists crowded into St. Mark's Square to observe ABC's Sam Donaldson do a standup on Sunday evening.

Watching the spectacle in apparent anonymity from a nearby table at the famed Florian Cafe was West German Chancellor Helmut Kohl.

At least Kohl recognized Donaldson. Today, Reagan answered a question from CBS correspondent Bill Plante by calling him "Sam." The president afterward apologized and promised to address Donaldson as "Bill" the next time he answered a question.