A subsea fluid pressure increasing machine comprising: a first elongated member rotatable about a longitudinal axis; a motor system mechanically engaged to the member so as to rotate the first elongated member about a central longitudinal axis in a first rotation direction; a first plurality of impeller blades each impeller blade having a leading edge, a trailing edge and a first chord line defined by a line between the leading and trailing edges, each impeller blade being fixedly mounted to the first member such that a first chord angle defined by an angle between the first chord line and the first rotation direction is less than or equal to a stall angle at which a maximum force is exerted on a subsea fluid in a direction primarily parallel to the longitudinal axis when the first member is rotated in the first rotation direction; a second elongated member rotatable about the longitudinal axis in a second rotation direction being opposite to the first rotation direction; and a second plurality of impeller blades fixedly mounted to the second member such that the first plurality of impeller blades is interleaved with the second plurality of impeller blades, each impeller blade of the second plurality of impeller blades having a second chord line defined by a line between leading and trailing edges thereof and a second chord angle defined by an angle between the second chord line and the second rotation direction, which is less than or equal to a stall angle at which maximum force is exerted on the subsea fluid in a direction primarily parallel to the longitudinal axis when the second member is rotated in the second rotation direction; wherein the elongated members (318, 330), the motor system, and the first and second pluralities of impeller blades (320, 340) are configured for subsea deployment; the subsea fluid pressure increasing machine is characterised in that each impeller blade of the first and second pluralities of impeller blades (320, 340) has multiple orifices that extend through the impeller blade from a high pressure side of the impeller blade to a slot that extends to a low pressure side of the impeller blade that effectively increases the stall angle of the impeller blade. a first elongated member rotatable about a longitudinal axis; a motor system mechanically engaged to the member so as to rotate the first elongated member about a central longitudinal axis in a first rotation direction; a first plurality of impeller blades each impeller blade having a leading edge, a trailing edge and a first chord line defined by a line between the leading and trailing edges, each impeller blade being fixedly mounted to the first member such that a first chord angle defined by an angle between the first chord line and the first rotation direction is less than or equal to a stall angle at which a maximum force is exerted on a subsea fluid in a direction primarily parallel to the longitudinal axis when the first member is rotated in the first rotation direction; a second elongated member rotatable about the longitudinal axis in a second rotation direction being opposite to the first rotation direction; and a second plurality of impeller blades fixedly mounted to the second member such that the first plurality of impeller blades is interleaved with the second plurality of impeller blades, each impeller blade of the second plurality of impeller blades having a second chord line defined by a line between leading and trailing edges thereof and a second chord angle defined by an angle between the second chord line and the second rotation direction, which is less than or equal to a stall angle at which maximum force is exerted on the subsea fluid in a direction primarily parallel to the longitudinal axis when the second member is rotated in the second rotation direction; wherein the elongated members (318, 330), the motor system, and the first and second pluralities of impeller blades (320, 340) are configured for subsea deployment; the subsea fluid pressure increasing machine is characterised in that each impeller blade of the first and second pluralities of impeller blades (320, 340) has multiple orifices that extend through the impeller blade from a high pressure side of the impeller blade to a slot that extends to a low pressure side of the impeller blade that effectively increases the stall angle of the impeller blade.