"She was really nice and funny. We always played games together," Noah said.
The junior lifeguard program was canceled on Wednesday to remember the 11-year-old victim and will resume on Thursday.
Officials said she was the first junior lifeguard to die during training in the program's 45-year history.
An autopsy performed Wednesday morning found that Allysa died of sharp force injury to her back and leg.
Authorities said as many 25 other junior lifeguards were in the water at the time of the accident. They had been practicing a speed drop, which is when the lifeguard drops off the boat to reach a swimmer in distress.
"We hold on to the handles of the back of the boat and crouch in a ball on the step, and then when they tell you to, you let go and you just fall backwards into the water," Noah said.
Officials said Allysa and another girl became separated from the group for some reason.
The waters were choppy when Allysa was hit by the boat.
She was rushed to the hospital, with cuts that authorities say were mostly caused by the propeller.
Authorities said the 53-year-old Marine Safety Lt. Greg Crow was driving the boat. He is now on leave from the department that he's served for more than 30 years.
There was also a Marine Safety officer and another lifeguard in the boat at the time of the accident.
"It's a devastating tragedy for the family," said Chief Kyle Lindo from Huntington Beach Marine Safety. "I can't imagine what they're going through, and our deepest sympathies and condolences go out to the family