At Ocean Beach - the waves are unpredictable, the undertow is almost invisible and the water is about 60 degrees.
Seventeen San Francisco firefighters will be going through five days of training. The fire department was picked to do this training because they are on duty 24/7.
The trainees wear protective gear to prevent hypothermia in the water and they are taught not to fear the undertow and the other things in the water - just to go with the currents until you find a spot where you can pop up or wait to get back to the beach. They are also learning above all not to panic.
"What we are doing today is we are going to be putting victims out in the water. Like I say, it's the final day, it's kind of a test day. We have been testing these guys from a pool, a cold water environment, now we are out at Ocean Beach - which is where a lot of these rescues happen," said Robert Styles, San Francisco fire department.
The training is certified by the National Lifeguard Association - the fire department is very proud of the fact that 300 of their 1,600 firefighters are certified.