A pump for immersion in a fluid includes—an inductor having guide vanes to induce linear fluid flow; —a rotor with a central, flared body, this rotor being downstream of the inductor relative to the direction of fluid circulation; —a helical blade provided around the central body; this helical blade having a flared external profile and having turns with an increasing winding pitch, and the internal casing volume being complementary to the flared helical blade, —a casing around the rotor; —a diffuser having blades making the flow of fluid linear and disposed downstream of the rotor to evacuate the fluid from the rotor; and—a diffuser insert having blades and an outlet orifice with a diameter less than the inlet diameter of the diffuser insert, the blades directing the fluid from the diffuser towards the orifice to increase the orifice outlet pressure.