A method of manufacturing a foil, selected from a hydrofoil and an aerofoil, comprised of a fibre-reinforced resin matrix composite material, the method comprising the steps of: a) providing an elongate moulding tool having a mould surface which extends along, and is curved along, a length direction of the elongate moulding tool, the length direction extending between opposite first and second ends of the elongate moulding tool; b) providing a plurality of preform layers, each preform layer comprising a fibrous reinforcement at least partly impregnated by a resin, each preform layer having a respective two-dimensional shape and dimensions; c) positioning a first preform layer on the mould surface; d) sequentially positioning further preform layers on the first preform layer to build-up an elongate first shaped body comprising a first laminated stack of preform layers on the mould surface, the first shaped body having an inner surface in contact with the mould surface, whereby an outer surface of the first shaped body, remote from the mould surface, has a first curved contour profile along a length of the first shaped body and a second curved contour profile transverse to the length of the first shaped body, each of the first and second curved contour profiles being formed by varying the number of preform layers at positions along the respective contour profile; e) curing the first shaped body to form a first foil part comprised of a fibre-reinforced resin matrix composite material formed from the preform layers; f) removing the first foil part from the mould surface to expose the inner surface; g) sequentially positioning further preform layers on the inner surface to build-up an elongate second shaped body on the first foil part to form an elongate unitary body having a length defined between opposite longitudinal ends of the unitary body, the unitary body being curved along the length of the unitary body, wherein the second shaped body comprises a second laminated stack of preform layers on the inner surface, whereby an outer surface of the second shaped body, remote from the inner surface of the first foil part, has a third curved contour profile along a length of the second shaped body and a fourth curved contour profile transverse to the length of the second shaped body, each of the third and fourth curved contour profiles being formed by varying the number of preform layers at positions along the respective contour profile (92,94); and h) curing the second shaped body on the first foil part comprising the elongate unitary body to form an elongate foil, selected from a hydrofoil and an aerofoil, comprised of a fibre-reinforced resin matrix composite material formed from the preform layers. a) providing an elongate moulding tool having a mould surface which extends along, and is curved along, a length direction of the elongate moulding tool, the length direction extending between opposite first and second ends of the elongate moulding tool; b) providing a plurality of preform layers, each preform layer comprising a fibrous reinforcement at least partly impregnated by a resin, each preform layer having a respective two-dimensional shape and dimensions; c) positioning a first preform layer on the mould surface; d) sequentially positioning further preform layers on the first preform layer to build-up an elongate first shaped body comprising a first laminated stack of preform layers on the mould surface, the first shaped body having an inner surface in contact with the mould surface, whereby an outer surface of the first shaped body, remote from the mould surface, has a first curved contour profile along a length of the first shaped body and a second curved contour profile transverse to the length of the first shaped body, each of the first and second curved contour profiles being formed by varying the number of preform layers at positions along the respective contour profile; e) curing the first shaped body to form a first foil part comprised of a fibre-reinforced resin matrix composite material formed from the preform layers; f) removing the first foil part from the mould surface to expose the inner surface; g) sequentially positioning further preform layers on the inner surface to build-up an elongate second shaped body on the first foil part to form an elongate unitary body having a length defined between opposite longitudinal ends of the unitary body, the unitary body being curved along the length of the unitary body, wherein the second shaped body comprises a second laminated stack of preform layers on the inner surface, whereby an outer surface of the second shaped body, remote from the inner surface of the first foil part, has a third curved contour profile along a length of the second shaped body and a fourth curved contour profile transverse to the length of the second shaped body, each of the third and fourth curved contour profiles being formed by varying the number of preform layers at positions along the respective contour profile (92,94); and h) curing the second shaped body on the first foil part comprising the elongate unitary body to form an elongate foil, selected from a hydrofoil and an aerofoil, comprised of a fibre-reinforced resin matrix composite material formed from the preform layers.