Whirlpools and boils
Also: boil, whirlpool
Whirlpools are rotating currents, often on eddy lines. A boil is water welling up from below and spreading out on the surface.
Both make the boat restless and can turn it. Stay calm, keep stable with paddle strokes and brace if necessary.
Sources and further reading
Research as of 13 Nov 2026. We have marked manufacturer information as such.