Under Keel Clearance (UKC)
Abbreviation: UKC
The vertical distance between the ship's deepest point + the seabed — a company-set safety-margin parameter for shallow-water navigation.
Regulatory detail & full definition
Under Keel Clearance is the vertical distance between the ship's deepest point + the seabed. Company + charter-party + port-authority policy sets minimum UKC — commonly 10-30% of draft in open water, higher (~15%) in transit channels, terminal-specific in port. UKC calculation must include squat + heel + wave allowance + tide + swell + hydrographic uncertainty. Under-keel-clearance policy failures + misjudged squat are among the top-3 grounding-casualty causes.
Authoritative source: OCIMF Publications ↗
Related
Source: OCIMF + IACS Guidance
High confidence
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