Matthew Miller, 16, and Gavin Powell, 17, told their families they were going rafting in a nearby aqueduct or creek at about 2 p.m. Saturday, Contra Costa County Sheriff's Office spokesman Jimmy Lee said.
The boys, who were both juniors at Las Lomas High School in Walnut Creek, were supposed to meet a friend at a designated location, but they failed to arrive two hours later, Lee said.
Their bodies were found Sunday morning in the Walnut Creek waterway, which is located in Concord, prompting grieving students and community members to set up a Facebook page remembering the boys.
A candlelit memorial walk has also been scheduled for Wednesday at 6 p.m. at Sutherland Open Space. As of 5 p.m. today, more than 400 people had responded on the Facebook event page that they plan to attend.
Miller, who was recalled by many as an accomplished swimmer and cross-country runner, was also remembered for his intellect, artistic skill and energetic spirit.
"I couldn't believe someone as lively, creative, talented, giving, energetic and as genuinely kind as you could really be gone," one student wrote on the memorial page.
"Your artwork amazed me," wrote another student.
Powell, whom many admired for his kempt facial hair, was remembered for his musical talent and gregarity.
"He was always one of the friendliest kids on the court," one student wrote. "He didn't always come out to compete, just to have fun and make friends, which he excelled at."
In the tight-knit Las Lomas community, even students who said they didn't know the boys were rattled by their loss.
One student said she could tell by reading the stories on Facebook that the two "were truly something special. In your lives, and now in your deaths, you have made an immense impact on our community and our lives."
School officials from Las Lomas High School were not available for comment today due to the observance of Presidents Day.
The boys were reported missing by their families just after midnight Saturday. The sheriff's office announced today that the boys died of asphyxia due to drowning.
Neither boy reportedly used a flotation device, according to the sheriff's office, but Lee said they were wearing helmets.