hydraulic
hy-DRAW-lik
A recirculating current formed when water flows over a ledge or dam and curls back on itself, trapping anything caught in the cycle. The most dangerous are "keeper" hydraulics — uniform, river-wide features with no escape route. Low-head dams create the deadliest hydraulics because they look benign from upstream.
Etymology
From Greek hydraulikos, relating to water pipes. The paddling usage captures the mechanical, impersonal force of the recirculating water.
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