The accident happened in Malibu last weekend, and 13-year-old Christopher has reportedly been in the ICU for days.
According to People magazine, Christopher Schwarzenegger was injured while boogie boarding, suffering a collapsed lung, broken bones and broken ribs.
"It has been a very scary week, Christopher is surrounded by his family and friends," Shriver and Schwarzenegger said in a joint statement.
According to the statement, Christopher is expected to make a full recovery.
"On behalf of our entire family, we want to sincerely thank the paramedics and lifeguards who responded so swiftly, as well as the doctors, nurses, emergency room and hospital staff who have cared for our son," the statement says. "They have been extraordinary to him and to us. We thank everyone for their thoughts and prayers and ask for respect and privacy for Christopher and our family."
The couple's 17-year-old son Patrick tweeted on Friday, "Thank you everyone for your messages about my brother. This kid is strongest kid I ever seen. Keep praying."
Katherine Schwarzenegger, 21, also tweeted support for her little brother.
"Thank you guys for ur concern and prayers for my baby brother! He's a tough little guy and getting better! Please keep praying for him! Xo," she said in the tweet.