The lake bed beneath the water has nearly no visibility, which meant human divers had to basically search by feel.
The lake itself is 1,200 acres and can reach depths of up to 130 feet.
Previously Friday afternoon, Captain Eric Buschow briefed the media about how the research for Rivera, who disappeared Wednesday all through a boating excursion with her son on the lake, is progressing.
From the sound, a girl told that the 911 operator her spouse had been among the folks who found the ship on Lake Piru which Rivera had hired along with her husband, Josey.
The boat that was rented by Naya Rivera
"This is the recording from the security camera at the boat launch when Naya Rivera and her son arrived to rent a pontoon boat at Lake Piru", deputies said in a release Thursday night.
Rivera was missing for over 24 hourswith a hunt now under way in the lake in southern California where she went missing.
Josey, Rivera's son told the authorities that he along with his mother were swimming in the lake while he got back on the boat, his mother was not there. "Again, there's a lot of shrubbery and sticks that we have to break through as we're going through, so it's kind of a Braille search".
The 4-year-old was discovered sleeping alone on the boat hours later, reportedly telling police his mum had "jumped into the water but didn't come back up". In that area there are a lot of trees and plants and such that can cause entanglements. "Makes it unsafe for divers and a complicated search", he said.
Sgt Donoghue added: "If we thought for a moment that there was any chance she could be on land somewhere, if we had any other clues or corroborating information that led us in that direction, we would do that and we would be out there searching and looking".
"It depends", Donoghue replied when asked if Rivera's body will be recovered if she did indeed drown. Naya's mom, Yolanda, and her younger brother, Mychal, were at the dock where Naya's boat departed Wednesday - only Yolanda was on her knees with her arms stretched out toward the water, and her pain is palpable. "It's made me a much more observant person", she said at the time.