Checking keel clearance, charted depth against draught

Charted depths are measured from chart datum, which in tidal waters is mean low water springs, so there is usually more water there than shown, though now and again there is less. On inland waters the level rises and falls with rain and wind, and in river estuaries shifting sediment adds to that.

Half a metre of keel clearance is the lower limit for calm water. In waves the keel dips deeper still, and in a persistent offshore wind the level drops measurably below the charted figure.

Grounding is the most frequently reported cause of claims. We cover it from Basis-Plus upwards under the comprehensive hull cover, including consequential damage to rudder, shaft and gearbox, and where damage is suspected we also pay for the craning needed to inspect the boat.