Rocker

Rocker describes the amount of upward curve built into a kayak's hull along its length, from bow to stern, when viewed from the side. A hull with a lot of rocker looks like a banana, curving up noticeably at both ends, while a hull with little or no rocker sits nearly flat and straight along the keel line from front to back.

More rocker lifts the ends of the kayak out of the water, which shortens the effective waterline and lets the boat pivot and turn quickly, at the cost of tracking in a straight line. That tradeoff is why whitewater kayaks, built to spin and maneuver in fast, chaotic current, are heavily rockered, while touring and sea kayaks, built to cover distance efficiently, use flatter hulls with minimal rocker.

Rocker also affects how a hull handles waves: more rocker helps a bow lift over an oncoming wave or wake instead of plowing through it, which is useful for whitewater and surf but less important for flat lake paddling. When comparing kayaks for a specific use, rocker is worth checking alongside length and width, since two boats of the same length can behave very differently in current or chop depending on how much curve is built into the hull.