"This is considered to be a horrible accident," Ventura County Sheriff's Department officials said, expressing that no foul play was suspected.
The department said it responded to a report of a boy alone on a boat around 4:48 p.m. Officers on scene found the child, but no information was immediately released about the child's condition.
Rivera, 33, and her son went swimming but the actress did not get back on the boat, the sheriff's department said. The boy had a life vest on but it is believed that Rivera did not, as a life vest was found on board the boat.
The boy was found sleeping on board the pontoon boat about three hours after it was rented, officials said.
A dive team and air unit were deployed to search for Rivera, the VCSD said.
Dive teams suspended their search late Wednesday, planning to resume it at daybreak on Thursday. As of Wednesday night, the operation was being called a search and rescue operation.
Investigators said they found Rivera's purse and wallet on board the boat, along with food.
Rivera’s 4-year-old son is from a marriage with actor Ryan Dorsey. The couple finalized their divorce in June 2018 after nearly four years of marriage.
She called her young son "my greatest success, and I will never do any better than him" in her 2016 memoir "Sorry Not Sorry."
The actress was engaged to rapper Big Sean in 2013, but their relationship ended a year later. The pair met on Twitter and collaborated musically, with the rapper appearing on Rivera’s debut single "Sorry."
