"Today was hard. I think he's exhausted," his mother, Maureen McGowan, said Friday evening. "Two ambulance rides and a plane ride are probably a lot for him."
The 18-year-old's struggles since breaking his neck on Aug. 10 have been chronicled almost daily in videos posted on You Tube and Facebook.
They include an especially poignant moment when his brother, Charlie McGowan, 8, sees him for the first time in the hospital.
"You're taking over. Now you're faster at running. You're quicker," Danny tells the boy. "You're the man of the house now."
At times, in his daily updates, Cox displays a remarkable attitude and even a little humor as he lies in bed, unable to feel his legs or most of his body.
"I'm doing a lot better today," he says on Day Three of his hospitalization, lying immobilized. "I can, you know, talk a lot easier and swallow.
"I can't really move my legs or arms at all still. And I have terrible itching all over. Those are pretty much the only bad things. Other than that, it's OK."
During his high school years, Cox shared much of his life on social networking sites, so doing so now is almost natural for him, said his mother.
A website, www.DannyCox888.com, displays the videos and provides a way for people to donate for the costs of his rehabilitation not covered by his Kaiser medical insurance.
One photo shows a smiling Cox prior to his accident, when he was a member of the Petaluma High School track team. He is holding two of the girls on the team, one on each arm.
"He's a great kid," his track coach Jim Lynch said Friday night. "He's probably one of the more talented and all-around athletes I've coached here, in the last seven years I've been here."
Physically gifted, the active young man was a long jumper, high jumper and hurdler.
The accident at Lake Tahoe was baffling for his family and friends. He ran into the lake and when he dove in - what he described as more of "flat dive," or belly-flop — his head struck bottom. He broke his neck and damaged his spinal cord.
The Petaluma community has rallied to help. Stinger Sportswear in Petaluma as of Friday had distributed nearly all the 50 t-shirts it was giving to people who donated $100 or more to the Danny Cox Rehabilitation Fund at First Community Bank.
A bake sale held by some of Cox's neighbors collected more than $3,100. A lemonade sale raised another $1,000, according to Maureen McGowan.
Cox's progress is day to day, measured by such things as being able to eat solid food.
He has feeling in his biceps, triceps and wrists, and is able to lift things.
The philosophy of the medical staff, said McGowan, is "hope for the best, but plan for the worst.
"They want him to get independent, mobile and take care of his own needs — towards being self-sufficient, less dependant and able to live on his own."
She said her son is expected to be at the Kaiser spinal rehabilitation center in Vallejo at least six weeks.
Any feeling that returns to his body is likely to come back within two months, she said.