dig a rail

When the surfboard's rail (edge) unexpectedly catches or "digs" into the water during a ride, abruptly slowing the board down and making it temporarily impossible to control. The surfer, after digging a rail, is either put off balance or chucked off altogether. Digging a rail is most likely to happen when the water surface is choppy, if there's backwash or any kind of lump running across the surf ...