Artillery Shell Casings Cause a Scare at Beaches : Holiday: Dozens of ammunition crates are spotted in the water and on the shores, but they are found to be harmless. Thousands flock to the sands.

Thousands of people headed to Orange County beaches on the final day of the Fourth of July weekend, enjoying the mild weather and, in some spots, thinner crowds. In what may have been the only untoward event, dozens of crated Naval artillery shell casings washed up on state and city beaches, giving authorities a brief scare until they were found to be harmless.

Boaters first spotted the ammunition crates offshore and alerted officials about 2 p.m. Sunday, Marine Safety Lt. Steve Seim said. Lifeguards roped off a section of surf at Huntington Beach until a county bomb squad and Navy officials determined that the shell casings--each about 20 inches long, four inches in diameter and coated with a brown waxy substance--presented no danger.

About 12 ammunition crates containing three shell casings each washed up on the city beach north of Beach Boulevard, the state beach between 13th and 14th streets, and on Bolsa Chica State Beach. Newport Beach Marine Safety officers also found what they believe to be a similar shell casing on their shore.

Boaters said they saw about two dozen crates floating offshore as far south as Dana Point and as far north as Los Angeles County, U.S. Coast Guard Petty Officer James Bride said. The Coast Guard notified Navy officials of the boxes’ positions, Bride said.

Seim said the casings appeared to have come from San Clemente Island. Navy officials could not be reached for comment Monday.

The ammunition crates that floated ashore didn’t seem to bother beach-goers, however.

Many lifeguards said the turnout Monday rivaled those for Saturday and Sunday.

“We had moderate surf, a pretty good crowd, and it was a great holiday weekend at the beach,” San Clemente Marine Safety Officer Steve Lashbrook said.

At Huntington State Beach, several tanned surfers hopped out of their trucks and headed toward the water, surfboards beneath their arms, only to stop at the parking lot’s edge and stare with disappointment at the hundreds of swimmers and waders in the water.

“Oh maaaaaaaan,” one teen-ager said as he clutched his board. The youths turned around and left as quickly as they had come.

But the crowds did not bother Mele Purcell-Tua’one, one of about 60 members of a church group from Hacienda Heights. Group members were there tossing water balloons, hopping in sack races and playing volleyball.

Purcell-Tua’one was more concerned about the weather.

“We expected it to be a little hotter,” she said as smoke wafted from a barbecue grill piled high with chicken. “But as long as it’s not raining, it’s OK.”

Residents enjoyed mild weather around the county Monday. Santa Ana, Anaheim, Dana Point and El Toro each reported a high temperature of 79 degrees, said Curtis Brack, a meteorologist with WeatherData, which provides forecasts to The Times. Newport Beach reported a high of 69 degrees. Lows ranged from the low to middle 60s countywide.

For today, county residents can expect low morning clouds that should clear away in the afternoon, and temperatures in the 70s to low 80s, Brack said.

Although the waters were calm Monday, rescues kept many lifeguards busy.

“We’ve had about 55 rescues today, and it’s only about 3 o’clock,” said Craig Lumb, a lifeguard at Huntington State Beach. Lumb said 75 people were rescued Sunday. The total for Saturday was 225, partly because of rip currents.

San Clemente lifeguards reported 50 rescues Monday, more than usual.

For some areas, the last day of the Independence Day weekend brought a decline in beach-goers. Salt Creek, Sunset and Aliso beaches only had about 20,000 visitors, said U.S. Ocean Safety lifeguard Steve Mosher. Some attributed the thinner crowds to the mild weather, and others surmised that many residents had traveled out of town for the weekend.

Traffic was light on most freeways, California Highway Patrol officials said, although some jams were reported near beach areas.