Rivera rented the boat at Lake Piru in Ventura County at around 1 p.m. Her son was found safe by another boater three hours later, according to KCAL-TV in Los Angeles.
Authorities have been searching by air and using dive teams amid a search and rescue operation for the 33-year-old actress, KNBC-TV reported.
Rivera and her son went swimming – he was wearing a life jacket but she wasn’t – and he got back into the boat but she didn’t, the sheriff’s department said, according to KNBC.
Rivera is best known for playing Santana Lopez on “Glee” and most recently has been in YouTube’s “Step Up: High Water.”
This is a developing story. Please check back for updates.