A San Francisco Fire Department training vessel, Rescue Boat 1, was overturned by a single rogue wave Saturday morning, throwing seven firefighters into the surf. As ABC 7 reports, the situation turned quickly scary despite the fact that the firefighters were all experienced swimmers, and four firefighters were taken to the hospital to be treated for hypothermia and minor injuries. One remained there overnight.

San Francisco Deputy Fire Chief Mark Gonzales says that conditions started out pretty calm for the 30-foot boat. "Conditions were calm, as I understand it. What I do understand there was a big wave that came up, what some might call a rogue wave came and flipped the boat," he tells the station.

According to KRON 4, "Good Samaritans in fishing boats rescued two firefighters," and "Two others were able to swim ashore and rescuers with the fire department helped the remaining three."

This all happened around 11:15 a.m. near the Cliff House, and per the Chronicle, the cause of the capsizing is under investigation.