Which hazard is defined by water flowing beneath a rock ledge?

• A. Whirlpool risk
• B. Tidal race
• C. Undercut rock hazard
• D. Overfall

Answer: (C)

Undercut rock hazards are the ones where water is flowing under a rock ledge, carving a hollow beneath it. That hollow can create strong, recirculating or suction currents that pull a kayak and paddler back toward the rock, sometimes trapping you under the ledge or against the base. The danger is often hidden from the surface, so you might not see the hazard until you’re right above it, which makes it easy to get pulled in or flipped. The safest approach is to give any rock ledges a wide berth and avoid paddling over the base where water is rushing underneath. Scout the area, watch for signs of backwash or a cave-like undercut, and approach with caution from a safe distance. This distinguishes it from a whirlpool (circular swirling water), a tidal race (a rapid, turbulent surge across a narrow space), or an overfall (water dropping over a ledge and creating a breaking surface wave).