Naya Rivera's Step Up Costars Remember Their 'Sweet' Friend: 'Her Love Matched Her Toughness'

Naya Rivera left a lasting impression on everyone she met.

On Monday, the former Glee actress was declared dead five days after she went missing during a boating trip at Southern California's Lake Piru with her 4-year-old son Josey, whom she shared with ex-husband Ryan Dorsey. After an autopsy had been conducted, the Ventura County Medical Examiner announced Tuesday that her cause of death was accidental drowning. She was 33.

In this week's issue of PEOPLE, stars from YouTube series Step Up: High Water open up about their "sweet" friend and how their late costar impacted their lives.

• For more about Naya Rivera, pick up this week's issue of PEOPLE, on newsstands Friday

“I call her Slugger, because her love matched her toughness," Faizon Love says. "She talked with her eyes. On tough days we would give each other a pound, As if to say, 'Let’s keep it movin.'' On good days, she would hit me with the wink like she were saying, 'I’m still fighting but today is a good day.' "

For Lauryn Alisa McClain, who starred in the first season, Rivera was a "bright light for me when I was in a dark place," she says.

"Never judge a book by its cover," says McClain. "When I looked at Naya, I saw her spirit. She had one of the most innocent, purest spirits that I have ever come across to this day. She was so sweet. It’s very easy to judge someone. She was definitely a bright light for me when I was in a dark place. She made things better when she was around."

RELATED: Glee Star Naya Rivera Dead at 33 After Disappearing on Boating Trip with 4-Year-Old Son

Other cast members of the show, which is gearing up for its third season on Starz, also expressed their condolences on social media.

Terrence Green posted multiple tributes to his Instagram Stories, including a moment in which he put his hand in the water of Lake Piru and a throwback clip of Rivera singing "Amazing Grace."

Terrence Green/instagram Terrence Green's Instagram Story post

RELATED: Naya Rivera’s Body Was Found Shortly After Glee Costars ‘Prayed for Her’ at Lake’s Edge: Police

Marcus Emmanuel Mitchell posted a Glee clip of Rivera singing "Santa Baby," with the caption, "Our sweet friend, we love you."

Last week, Rivera was reported missing after renting a pontoon with Josey. When the boat became overdue for return after its three-hour rental, staff found it at the north side of the lake, with Josey wearing a life jacket, sleeping alone on board. An adult life jacket, believed to be the one provided to Rivera, was still on the boat. One day later, police announced she was presumed dead, maintaining they considered her disappearance to be "a horrible accident."

After Rivera's body was found on Monday, Ventura County Sheriff Bill Ayub recounted what the actress' young son told authorities about the tragic accident.

"We know from speaking with her son, that he and Naya swam in the lake together at some point during their journey. It was during that time that her son described being helped into the boat by Naya, who boosted him onto the deck from behind," the sheriff said Monday afternoon during a news conference. "He told investigators that he looked back and saw her disappear under the surface of the water."

Ayub said that "there are a lot of currents on the lake that appear particularly in the afternoon" and that authorities believe she disappeared in the "mid-afternoon."

Gregg DeGuire/Getty Images Naya Rivera and son Josey

"The idea perhaps being that the boat started drifting, it was unanchored, and that she mustered enough energy to get her son back onto the boat, but not enough to save herself," Ayub said.

RELATED: Naya Rivera 'Mustered Enough Energy' to Get Son on Boat but 'Not Enough to Save Herself': Police

He also expressed his condolences to the actress' loved ones during this heartbreaking time.

"As you can imagine, it has been an extremely difficult time for her family throughout this ordeal, as fathers, mothers, sons and daughters, our hearts are with them and we share in their grief for Naya’s loss. We have been in direct contact with the family throughout this entire time, and we’ve kept them updated on the progress of our search efforts throughout," said Ayub. "Our hearts also go out to Naya’s many friends and fans, who have been holding out hope for the best over the last few days."