A port that lies on the banks of a river. See also canal port, seaport, estuary port.

A horizontal movement in the upper layers of the sea, caused by wind.

A horizon produced by bubble, gyro or mercury trough to allow measurement of altitude of celestial bodies.

A buoy placed to mark a special position; in particular, near a light-vessel, to check its position.

The height above the datum for heights of the highest part of the underside of the span of a bridge, or the lowest part of an overhead cable. the vertical clearance of fixed bridges is measured from t [..]

A feature is said to be submerged if it has sunk under water, or has been covered over with water.

Either of the two points at which the Sun crosses the equator: or the dates on which these occurrences take place.

The sector, or sectors, in which a light is visible from seaward.

The least depth within the limits of a channel: it restricts the safe use of the channel to draughts of less than that depth.

The microscopic drifting animal life of the oceans including the larvae of the larger swimming animals and fish.