The San Jose family was playing in the water off 26th Avenue. Investigators believe the girl was knocked down by a wave. As she fell, she hit a large log on the sand. The surf then pulled her out to sea, trapping her under the log.
Deputy April Skalland of the Sheriff s Office said: "We've been having a lot of rain this week. The rivers will overflow, start getting debris -- logs trees, sticks -- and they start pushing them out to the ocean.
"And at that time, these things will start floating up on to the different beaches, and that's what we were seeing yesterday."
Family members tried but couldn't lift the log off the girl. Rescuers did, but the girl later died at the hospital.
"The log was pretty heavy, about a thousand pounds, water soaked and logged, so we're not sure right now what happened to her exactly what the cause of death was," Skalland said. "But we're still going to have to do some research into that."
Local surfers say beach visitors don't always know about the danger of debris that lurk in the water or on the sand.
"Normally it's just kelp, but yesterday unfortunately it was something bigger, so it's just really important to be careful and if you can, swim near a lifeguard," surfer Matt Nauman said.
The Santa Cruz County Sheriff's Department is not releasing the name of the San Jose family. The parents and a sibling were with the girl when the accident happened.
