(Sandra Schorken)

Two men and a woman dove in to a California estuary Sunday to rescue a family, including two children, trapped in a vehicle about to submerge.

Andy Goodwin, Erik Schorken and Schorken's family were driving along the estuary in Oakland, Calif., on their way back from a Father's Day lunch when they noticed a woman frantically waving her hands and pointing towards the water.

"I said to my wife, 'I think someone might have gone into the water,'" Schorken told ABC News. "But no one was stopping."

Then they saw an ambulance, so Schorken decided to pull over and see what was going on.

It turned out the ambulance was there for another matter, but the car's occupants noticed people were trapped in the water, so Schorken, Goodwin and Tracey McCormick, who was also driving by the estuary at the time, jumped in and swam out to the scene.

"This car was 60 degrees up in the air; it was going nose down into the water," Schorken said. "I just kept swimming out there."

The mission soon appeared hopeless. Because the car's doors were locked, the would-be rescuers had no way of accessing the victims. Halfway towards the car, Goodwin swam back to the shore.

"I swam about halfway out and I realized I wasn't going to be able to do much," Goodwin told ABCNews.com.

McCormick said that when she reached the vehicle, the victims' hands "were on the windows screaming to get us out."

One of the paramedics had an emergency pocket knife designed to break through glass. She handed Goodwin the pocket knife. Goodwin subsequently gave it to McCormick, who gave it to Schorken after she had trouble with it. Schorken broke through the window, and he and McCormick took the family - a mother, a father, and two kids Schorken guessed were between the ages of 7 and 10 - 20 feet to shore.

As soon as they reached the land, the car completely submerged into the water.

"I looked behind me and the car was gone. I couldn't believe how fast it sunk," said McCormick.

The family was fine and was not taken to the hospital, the Oakland Police Department told ABC News.

KGO-TV reported the rescue Sunday, referring to Goodwin and Schorken as "good Samaritans."

Schorken spent nine years in Brazil as a missionary and is a pastor at his church in California. He and Goodwin are friends through their church.

Schorken's desire to put himself on the line, he said, stemmed from his faith.

"We're Christians," he said. "I just feel like were obligated to help. What if it was my wife in the car and my kids? I would want someone to help. You just act accordingly."

McCormick said it was never a question of whether she would help, but how fast she could get to the vehicle.

Although Schorken did not know the name of the family he rescued, he had their phone number and was planning on inviting them over for dinner.

Calls to the number Schorken provided went unanswered.

Johnna Watson of the Oakland Police Department said the family likely would not have survived without the help.

"Time is of the essence in a situation like this," she told ABC News. "By the time we arrived on scene the occupants were taken out. This made the difference between life and death."

Watson said there will be an investigation into the cause of the accident.