He believes the death was preventable and is suing them for wrongful death and negligent infliction of emotion distress, according to Us Weekly.
"(The boat) was not equipped with a safely accessible ladder, adequate rope, an anchor, a radio or any security mechanisms to prevent swimmers from being separated from their boats," the documents claim.
"Disturbingly, later inspection revealed that the boat was not even equipped with any flotation or lifesaving devices, in direct violation of California law, which requires that all pontoons longer than 16 feet be equipped with flotation devices."
However, a report from the Ventura County Medical Examiner-Coroner's Office claimed Josey was found on the boat with a life vest, but Rivera did not have one on when her body was found.
The suit further alleges that Lake Piru did not have "a single sign anywhere – not at the entrance, at the dock, at the popular swimming area of Diablo Cove, not anywhere – warning of the lake's strong currents, low visibility, high winds, changing water depths, underwater caves, ledges and drop offs, or the trees, brush and other debris that congest its waters due to the vastly changing water levels and winds".
In a full autopsy report released in September, which was obtained by People, Josey told investigators that his mother had counted "1, 2, 3" as they jumped off the boat together to swim in the lake.
"She helped him onto the boat and then he then heard (Rivera) yell 'help' and she put her arm in the air. She then disappeared into the water," the investigative report stated.
The report also outlines factors that may have contributed to Rivera's mysterious drowning death, which has been ruled as an accident. The actress suffered from vertigo – a condition that would get worse when she was in water.
Rivera "would have vertigo to the point of vomiting, but she learned to control the symptoms with antihistamines", the report stated.
According to Rivera's death certificate, issued three weeks after her death, she drowned "in minutes". No drugs or alcohol were found in her system.
Ventura County and United Water Conservation District have not yet addressed the lawsuit.
