What is "surf ski"

n. Long narrow water craft (about 18 feet long) seating one person, propelled by paddling with a two-ended paddle and incorporating a small rudder controlled by foot levers. Designed for recreation or competition in surf, especially surf life saving, but only for going straight out and in, not for surfing across a wave like a wave ski.

A surf ski is a long, narrow, lightweight kayak with an open (sit-on-top) cockpit, usually with a foot pedal controlled rudder.