Which hazard is defined as turbulent water from a submerged feature?

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

Answer: (C)

An overfall is water that flows over a submerged ledge or rock, forcing the water to tumble and become highly turbulent downstream. That sudden drop and the resulting chaotic flow is exactly what “turbulent water from a submerged feature” describes, so this hazard is the one you’d expect to encounter when the water hides a submerged obstacle.

Whirlpools are circular rotating currents, undercut rock hazards involve suction or entrapment at the base of a rock, and tidal races are strong tidal currents that can create standing waves along shorelines. None of those specifically capture the turbulence produced by water tumbling over a submerged feature like an overfall.