A subway surfer was killed Wednesday as he tried to climb on top of an F train in Brooklyn, authorities said.

Christopher Serrano, 25, met his demise before he even got the chance to gain his balance, according to police sources.

He had been riding the train with a female friend when he went between two of the subway cars and began scaling the outside of the train sometime around 5 a.m., sources said.

Investigators believe Serrano may have been clipped by something as the train was rolling into or out of the Fourth Avenue/9th Street station in Gowanus, the sources added.

Police found the man lying dead on the roadbed a short time later, officials said.

It is believed Serrano was intoxicated at the time, sources said.