The woman and 5-year-old girl got caught up in a rip current. It happened at the south end of the beach where it is said to be deeper and more dangerous.
The Half Moon Bay Fire Department says it started out as a family enjoying a nice day at the beach.
"They were out in the surf line somewhere. Some were in their wetsuits and some were in bathing suits," said Half Moon Bay Batt. Chief Ari Delay.
At around 4 p.m. about a half dozen of them got swept away by a rip current. It was so strong, that at least three of them were carried about a quarter mile out to sea.
One person was able to reach the shore without any help, while bystanders helped a woman in her forties out of the water.
It took much longer to locate the 5-year-old girl. Emergency crews used a boat to find her.
"The United States Coast Guards and State Park lifeguards, as well as the Pillar Point Harbor Patrol, worked to find the 5-year-old child that was out in the ocean and they were able to extricate her after about 15-20 minutes of search," said Batt. Chief Delay.
The woman and the 5-year-old girl were airlifted to Standford Medical Center. Paramedics performed CPR along the way, but were unable to revive them.
Emergency personnel say the two were victims of a particularly dangerous section of Montara State Beach. They say the south end is known for its heavy waves, which surfers often use to get out to sea.
"We can be lulled into a sense of security on the beach that everything's great because it's a nice sunny day, but the ocean doesn't care whether it's sunny or windy or cold. It's treacherous out there and people are easily swept off their feet and taken out to sea," said Batt. Chief Delay.
Unless you are a strong swimmer and know how to get out of a rip tide, it is recommended that you stay out of these waters. It's something rescue crews like to emphasize as the Fourth of July holiday approaches.