The 33-year-old actress died during a boating trip at a Southern California lake with her four-year-old son in July. A medical examiner had previously ruled her death was an accident.
The Ventura County Medical Examiner’s Office has now released an investigative report into Rivera’s death, revealing new details about her final moments.
Rivera was a good swimmer, according to the report, and had made previous trips to Lake Piru.
She is said to have declined the offer of a life jacket when renting the boat on July 8, however the employee ensured the vest was on the vessel.
Before she disappeared, she and son Josey jumped into the water at an area known as Diablo Cove.
Shortly afterwards, the report states, Rivera pushed the boy back onto the boat. When the child looked back, he saw his mother put her arm in the air and shout “help,” according to the report.
Boat rental worker Bryan Tomaszewski went looking for the rented vessel when it was not returned on time and found Josey wrapped in a towel, wearing a life vest and asleep.
A spare adult-sized life jacket was also on the boat, along with Rivera’s possessions including her bag and mobile phone.
Rivera’s mother, Yolanda, told investigators the actress had planned to have a barbecue at the lake but changed her mind and rented a boat instead.
Rivera had no known medical history other than vertigo and a recent sinus infection, the report states. Her body was found floating on the surface of the lake on July 13.
The post-mortem report states the death was as a result of accidental drowning.
Rivera was best known for her “groundbreaking” portrayal of high school cheerleader Santana Lopez in Glee, an openly LGBT character who proved hugely popular with fans.
The actress’s devastated Glee co-stars were among those to pay tribute following her death.
In a statement, Rivera’s family described her as a “sassy angel”.
They said: “We are so grateful for the outpouring of love and prayers for Naya, Josey and our family over the past week. While we grieve the loss of our beautiful legend, we are blessed to honour her everlasting legacy and magnetic spirit. Naya was an amazing talent, but was an even greater person, mother, daughter and sister.”