A wave-powered pumping device (100, 176, 182, 200) for location in a body of water, the pumping device comprising: a submersible cylinder to be anchored to the bed of the body of water, the cylinder defining a bore; an underwater float acting on the cylinder, the underwater float being arranged to urge the cylinder into an upright orientation in the water; a surface float arranged to float at, or close enough to, the surface of the body of water in use to move up and down in the body of water in accordance with wave movement and tidal movement; and an elongate member depending from the surface float, the elongate member extending telescopically into the bore of the submersible cylinder to define a pumping chamber within the cylinder; wherein: the volume of the pumping chamber varies with wave movement in a pumping cycle to draw fluid into the pumping chamber on an upstroke of the elongate member and to pump fluid out of the pumping chamber on a downstroke of the elongate member; the length of the pumping chamber varies with tidal movement to adjust to changing tidal depth by extending or retracting the elongate member relative to the cylinder while effective pumping cycles continue across a tidal range without needing to move the cylinder with respect to the bed of the body of water; and to the extent that the elongate member is retracted into the bore of the cylinder, the elongate member occupies a majority of the cross-sectional area of the bore. a submersible cylinder to be anchored to the bed of the body of water, the cylinder defining a bore; an underwater float acting on the cylinder, the underwater float being arranged to urge the cylinder into an upright orientation in the water; a surface float arranged to float at, or close enough to, the surface of the body of water in use to move up and down in the body of water in accordance with wave movement and tidal movement; and an elongate member depending from the surface float, the elongate member extending telescopically into the bore of the submersible cylinder to define a pumping chamber within the cylinder; wherein: the volume of the pumping chamber varies with wave movement in a pumping cycle to draw fluid into the pumping chamber on an upstroke of the elongate member and to pump fluid out of the pumping chamber on a downstroke of the elongate member; the length of the pumping chamber varies with tidal movement to adjust to changing tidal depth by extending or retracting the elongate member relative to the cylinder while effective pumping cycles continue across a tidal range without needing to move the cylinder with respect to the bed of the body of water; and to the extent that the elongate member is retracted into the bore of the cylinder, the elongate member occupies a majority of the cross-sectional area of the bore. the volume of the pumping chamber varies with wave movement in a pumping cycle to draw fluid into the pumping chamber on an upstroke of the elongate member and to pump fluid out of the pumping chamber on a downstroke of the elongate member; the length of the pumping chamber varies with tidal movement to adjust to changing tidal depth by extending or retracting the elongate member relative to the cylinder while effective pumping cycles continue across a tidal range without needing to move the cylinder with respect to the bed of the body of water; and to the extent that the elongate member is retracted into the bore of the cylinder, the elongate member occupies a majority of the cross-sectional area of the bore.