Around 2 p.m., first responders received a report about a missing teen boy near Crissy Field.
San Francisco Fire Department said the boy was reported to be struggling in the water.
Authorities said the boy was at the beach with a group of friends who tried to rescue him when they saw he went under water. They called 911 when they could not find him.
Cristine Balderston was on the beach when it happened. She jumped in to help.
"I was in the water swimming around trying to find him for about five or 10 minutes before the rescue team got there," Balderston said. "I just wanted to help any way I could and I wish I would have been able to."
The boy reportedly did not know how to swim.
After about 90 minutes underwater, a rescue diver found the young man and brought him to shore. Paramedics tried to bring him back to life.
SFFD said he was transported to the California Pacific Medical Center, where he died.
With record heat across the Bay Area, more people are hitting the beaches. But safety is a top concern. At most San Francisco Beaches, there are no lifeguards.
"Why not throw some lifeguards here when the weather is like this, because you know the beaches get clogged," Matthew Stewart, who was at Crissy Field during the search and rescue, asked.
SFFD says it's important not to be fooled by a beautiful day.
"If you're coming to our coastlines, know before you go, our beaches are beautiful, however there are inherent dangers and hazards that are here," SFFD spokesperson Jonathan Baxter told reporters. "Always remember to swim with a friend, swim in groups. If you don't know how to swim, stay out of the water."
.@SFFDPIO confirms they have found the 14-year-old boy missing at Crissy Field Beach. He has been transported to California Pacific Medical Center. SFFD says chances are not in his favor, but multiple responders are working to bring him back to life.— Liz Kreutz (@ABCLiz) June 10, 2019
First responders have pulled someone from the water here at Crissy Field Beach. They are doing CPR now. pic.twitter.com/mElMfTJBNp— Liz Kreutz (@ABCLiz) June 10, 2019
Oh no! Was just at Crissy on Saturday. Hope firefighters find the missing swimmer. https://t.co/ZrFf7snAQA— Kate Larsen (@KateABC7) June 10, 2019
BAY RESCUE CRISSY FIELD REPORTED15 YO MALE MISSING LAST SEEN STRUGGLING IN WATER pic.twitter.com/FFDq6SW3Tx— SAN FRANCISCO FIRE DEPARTMENT (@SFFDPIO) June 10, 2019