The invention relates to a pump (1) which is to be implanted into a vessel or a heart, wherein the pump (1) is inserted into the vessel or the heart in a first state, in order to then be able to be functionally changed over to a second state, said pump having a drive part and a delivery part (FE), wherein the drive part is non-functional in the first state and becomes functional owing to the changeover to the second state, wherein the drive part has an electric motor, wherein the electric motor is in the form of a wet rotor, and wherein the rotor (R) of the electric motor is arranged separately from the stator (S) of the electric motor in the first state, and wherein the rotor (R) of the electric motor is moved into the stator (S) of the electric motor in the second state, wherein the rotor (R) can drive the delivery part (FE) in the second state.
