6:37 PM PT -- The Ventura County Sheriff just released security camera footage from the boat launch where Naya and her son rented a pontoon boat on the lake.
In the video, you see Naya pull up in her G-Wagon, and she gets out with a bunch of gear and walks with her son over to the boat launch. The two of them get in the pontoon and head off into the lake.
11:12 AM PT -- More than 80 people are currently involved in the search, which is utilizing helicopters, boats, ATV vehicles and ground personnel to try to locate Naya ... according to the Ventura County Sheriff.
Specialized dive teams from surrounding counties are also en route to help.
8:32 AM PT -- Authorities have just made it clear -- Naya is presumed dead and the search has now shifted from a rescue to a recovery mission. She went missing in water with only 5 to 9 inches of visibility, and authorities say the lake is filled with trees and debris on the bottom. Law enforcement says it typically takes 7 to 10 days for a body to rise to the surface.
5:29 AM PT -- Authorities are now saying they're treating the case as a possible drowning and they suspended the search overnight. The search continues at first light, but the Ventura County Sheriff says they now believe Naya may have lost her life in the lake.
Naya Rivera is missing on a Southern California lake after her toddler son was found alive, but alone on a boat ... TMZ has confirmed.
Ventura County Sheriff's deputies found the 4-year-old boy on the boat -- presumably rented by Naya -- shortly before 5 PM on Lake Piru, but Naya was not there. Law enforcement sources tell us her son, Josey Hollis Dorsey, told deputies his mom had jumped in the water ... but didn't come back up.
Divers immediately started searching the lake, but so far there's no sign of the "Glee" star. The search was suspended due to nightfall, but it's expected to resume Thursday, shortly after sunrise.
We're told Rivera's life jacket was still in the boat and Josey was asleep when the boat was first found. Josey is okay and is now with family members. Naya and the boy's father, Ryan Dorsey, divorced in 2018 and share custody of Josey.
On Tuesday Naya tweeted a pic of her kissing Josey with the caption, "just the two of us."