Janelle and Heather Hernandez started their Fourth of July weekend Thursday afternoon with a cruise across Modesto Reservoir on a jet ski.
The teenage cousins and their families from the Bay Area were camping out at the reservoir until Sunday for four days under the sun and in the water.
"We'll pretty much stay in the water," said 19-year-old Heather Hernandez. "It's too hot to do or go anywhere else."
Stanislaus County's water parks are expected to be filled with hundreds of visitors celebrating the Fourth of July, and park officials want to make sure they stay safe.
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"Bring a life jacket or some kind of flotation device, even if you think you're a good swimmer," said Stanislaus County sheriff's Sgt. Paul Yotsuya. "And bring plenty of water to drink. It's going to be one of the busiest weekends of the year."
Drownings and heat exposure are some of the major hazards that await visitors to Modesto and Woodward reservoirs. Yotsuya supervises the deputies who patrol the two reservoirs.
Modesto Reservoir, east of Waterford, has 2,800 acres for recreation with about 150 campsites. Woodward Reservoir, north of Oakdale, has 2,900 acres for recreation and 155 campsites. Yotsuya said most of the campsites at both reservoirs were reserved by Thursday.
Tony Reygoza, 51, of Brentwood and his family have been camping at Modesto Reservoir every Fourth of July for 15 years. He was lounging in a lawn chair and enjoying the view from his campsite Thursday.
"We like the boating, and we can keep our boats nearby," Reygoza said.
Visitors at both reservoirs are not allowed to have fireworks. The sheriff's deputies usually confiscate some fireworks from visitors each Fourth of July.
Reygoza said his family doesn't mind celebrating the holiday without fireworks.
Sheriff's officials say most of the hazards come from the water. Jet skis moving too fast or too close to swimmers and other watercraft is a major cause of injuries at the reservoirs, said sheriff's deputy Wayne Whitfield, who patrols Modesto Reservoir.
Last weekend, Amanda Nevarez, 19, of Joshua Tree in Southern California was injured after taking her first ride on a jet ski when she collided with another jet ski at Modesto Reservoir.
A common maneuver on the water, called "jetting" or "spraying," is when a jet ski makes a sharp turn, creating a spray of water for anyone nearby.
"The back end lifts out of the water and you lose control," Whitfield said. "That's what causes a lot of collisions."
Another dangerous personal watercraft maneuver is jumping the wake of a boat. Whitfield said the jumps can cause a collision if the watercraft is within 100 feet of the boat.
"I caught two guys doing it last week, jumping right behind the boat," Whitfield said.
Turlock Lake State Recreation Area deals with some of the same water hazards. But it's the cold water at the lake that can shock some swimmers and make it really tough for them to get back to shore, said Bill Lutton, park superintendent at Turlock Lake.
"We have the coldest water in the county," he said. "Even though it's hot outside, people need to remind themselves the water is colder than they think."
The water was about 60 degrees Thursday, which is about the average for July. Lutton said the water is cold because it flows from the bottom of Don Pedro Reservoir into the lake.
Turlock Lake is east of Waterford and south of Highway 132. By Thursday, its 62 campsites were reserved for the weekend.
Matt Francavilla, 53, and his family were launching their boat and setting up their campsite at the lake Thursday. They planned on camping until Sunday.
"We like the camping area," said Francavilla of Sunnyvale. "It's shady, and it doesn't get really crowded on the lake."
Lutton said life jackets are a necessity for adults and children on boats, personal watercraft and pretty much anyone else jumping into the lake.
"Even for the swimmers, and especially for inexperienced swimmers, you should have a life jacket on," Lutton said. "They think they're better swimmers than they really are."
Bee staff writer Rosalio Ahumada can be reached at email@example.com or 578-2394.