Chris Colfer has paid a moving tribute to his Glee co-star Naya Rivera following her tragic death a fortnight ago.

The actress drowned while swimming in California's Lake Piru with her young son, whom she is believed to have helped back onto their rented boat in her final moments.

In a 800-word essay published in trade magazine Variety, Colfer - Kurt Hummel on the musical drama - described his friend and former colleague as a "cool older sister" and "outstanding mother".

"The process of losing her has been such a nightmare, I find myself wondering if Naya was even real or if she was just a dream all along," he wrote. "How could a human being be that talented, that hilarious and that beautiful at once? How could one person be responsible for so much joy and be the subject of so many wonderful memories?"

He continued: "As a friend, you could talk to her about anything. She was the cool older sister you went to for advice, to blow off steam, or to get the hottest take on the latest gossip. Just being in Naya's presence made you feel protected and regardless of the situation, you knew she'd have your back. She was never afraid to stand up to authority, she always called out mistreatment where she saw it and she always told you the truth - even when it was hard to hear.

"For as long as I've known Naya, the thing she wanted most in life was to be a mother. She spent hours telling us what she was going to name her kids, how she was going to dress them and all the free babysitting she'd bamboozle out of us. When her son Josey was born in 2015, it was like a missing piece of Naya had finally arrived. Their connection was magnetic, their affection was radiant and I've never seen a person look happier than when Naya gushed over her little boy.

"Being a mom was perhaps Naya's greatest talent of all, and as her final moments proved, Naya was an extraordinary mother until the very end."

Rivera's body was located seven years to the day that Glee co-star Cory Monteith died of an accidental drugs overdose.