A flow modification device connectable to a generally cylindrical element adapted for immersion in a fluid medium, the device comprising: an elongate body having a length and a generally circular cross-section; a plurality of raised body portions disposed about and extending along the length of the elongate body , the raised body portions being arranged generally parallel to a longitudinal axis of the body and having a height between 2% and 10% of a diameter (D) of the body, wherein the diameter (D) of the body corresponds to the diameter of a circle intersecting the outermost edges of the raised body portions ; and an aperture extending through the length of the elongate body , the aperture being adapted to receive the generally cylindrical element such that the flow modification device is arranged about the cylindrical element; wherein the plurality of raised body portions are generally curved or rounded ridges which define respective grooved body portions therebetween, to provide a succession of raised and grooved body portions that present a substantially continuous geometry having no definite corners; and wherein the plurality of raised body portions are adapted to reduce vortex-induced vibration and/or drag on the cylindrical element when the device is connected to the cylindrical element and the connected device and cylindrical element are immersed in the fluid medium and there is relative movement between the connected device and cylindrical element and the fluid medium; wherein the plurality of raised body portions includes a first plurality of raised body portions disposed along a first length of the elongate body and a second plurality of raised body portions disposed along an adjacent second length of the elongate body , and wherein the second plurality of raised body portions are off-set about the longitudinal axis with respect to the first plurality of raised body portions such that the second plurality of raised body portions are not aligned with the first plurality of raised body portions. an elongate body having a length and a generally circular cross-section; a plurality of raised body portions disposed about and extending along the length of the elongate body , the raised body portions being arranged generally parallel to a longitudinal axis of the body and having a height between 2% and 10% of a diameter (D) of the body, wherein the diameter (D) of the body corresponds to the diameter of a circle intersecting the outermost edges of the raised body portions ; and an aperture extending through the length of the elongate body , the aperture being adapted to receive the generally cylindrical element such that the flow modification device is arranged about the cylindrical element; wherein the plurality of raised body portions are generally curved or rounded ridges which define respective grooved body portions therebetween, to provide a succession of raised and grooved body portions that present a substantially continuous geometry having no definite corners; and wherein the plurality of raised body portions are adapted to reduce vortex-induced vibration and/or drag on the cylindrical element when the device is connected to the cylindrical element and the connected device and cylindrical element are immersed in the fluid medium and there is relative movement between the connected device and cylindrical element and the fluid medium; wherein the plurality of raised body portions includes a first plurality of raised body portions disposed along a first length of the elongate body and a second plurality of raised body portions disposed along an adjacent second length of the elongate body , and wherein the second plurality of raised body portions are off-set about the longitudinal axis with respect to the first plurality of raised body portions such that the second plurality of raised body portions are not aligned with the first plurality of raised body portions. <EOS>