A subsea axial fluid pressure-increasing machine, comprising: an elongated member rotatable about a longitudinal axis; a motor system mechanically engaged to the elongated member so as to rotate the elongated member about the longitudinal axis in a rotation direction; and a plurality of impellers with blades each having a leading edge, a trailing edge, a suction side, a chord length (Lchord) and a chord line defined by a line between the leading and trailing edges, each impeller blade being fixedly mounted to the elongated member such that a chord angle (β 1 +AOA) of each blade defined by an angle between the chord line and the rotation direction is less than or equal to a stall angle at which a maximum force is exerted on a multiphase fluid in a direction primarily parallel to the longitudinal axis when the elongated member is rotated in the rotation direction, characterized in that each of the blades of the plurality of impellers is a one-element blade which has as stall angle enhancement features two axially spaced-apart slots which each form an inlet on the pressure side and an outlet on the suction side of the blade, which each are arranged radially along the blade to extend outwardly from a hub of the impeller toward radially outlying tips of the impeller blade, and which each effectively increase the stall angle of the impeller blades to effectively reduce a pressure peak or specific loading of the suction side of the blades, such that, compared to a reference impeller with 9 blades free from stall angle enhancement features, the chord length (Lchord) of each blade is reduced and thus the axial length (Laxial) of the impeller is reduced without exceeding a desired specific load, compared to a reference impeller with 9 blades free from stall angle enhancement features, and a number of blades is increased according to the reduction in the axial length such that a product of the number of blades and the axial length remains substantially constant, the number of blades being at least 10. an elongated member rotatable about a longitudinal axis; a motor system mechanically engaged to the elongated member so as to rotate the elongated member about the longitudinal axis in a rotation direction; and a plurality of impellers with blades each having a leading edge, a trailing edge, a suction side, a chord length (Lchord) and a chord line defined by a line between the leading and trailing edges, each impeller blade being fixedly mounted to the elongated member such that a chord angle (β 1 +AOA) of each blade defined by an angle between the chord line and the rotation direction is less than or equal to a stall angle at which a maximum force is exerted on a multiphase fluid in a direction primarily parallel to the longitudinal axis when the elongated member is rotated in the rotation direction, characterized in that each of the blades of the plurality of impellers is a one-element blade which has as stall angle enhancement features two axially spaced-apart slots which each form an inlet on the pressure side and an outlet on the suction side of the blade, which each are arranged radially along the blade to extend outwardly from a hub of the impeller toward radially outlying tips of the impeller blade, and which each effectively increase the stall angle of the impeller blades to effectively reduce a pressure peak or specific loading of the suction side of the blades, such that, compared to a reference impeller with 9 blades free from stall angle enhancement features, the chord length (Lchord) of each blade is reduced and thus the axial length (Laxial) of the impeller is reduced without exceeding a desired specific load, compared to a reference impeller with 9 blades free from stall angle enhancement features, and a number of blades is increased according to the reduction in the axial length such that a product of the number of blades and the axial length remains substantially constant, the number of blades being at least 10.