Rivera, 33, took a photo of her 4-year-old son, Josey, near a cove on Lake Piru about 90 minutes to two hours before he was found alone on a rented boat, US Weekly reported.

“We found where that cove was,” Robert Inglis of the Ventura County Sheriff’s Office Search and Rescue Team told the outlet.

Search crews used the background of the photo and the place where the boat was located to help zero in on where the actress might have gone missing, Inglis said.

“We did send our dive members to those two locations and searched those extensively,” he told the outlet.

He added that in many cases, there are witnesses “who see someone jumping off a boat so we know which area to search and we can find the body more quickly.”

But authorities said there are no witnesses in Rivera’s case.

“In this case, it really could be the whole lake. There are a lot of coves that have to be searched,” Inglis said.

The search for Rivera entered day six Monday on the lake, which about 56 miles northwest of downtown Los Angeles.

The actress is presumed to have drowned in the lake after her son told authorities that she went swimming but never climbed back onto their boat.