A submersible pump assembly (1), for arrangement in a shaft (2) or receptacle, includes a pump (3) and an electric motor (8) driving the pump (3) and a cable (5) for the supply of electricity. The cable is configured for being led out of the shaft (2) or receptacle at the upper side and for connection to an electricity source (7) outside the shaft or receptacle. The pump assembly (1) includes an electronics unit (9) which is configured to transmit a signal into the cable (5) and to detect a reflection signal at the surface (4) of the fluid (10) located in the shaft (2) or receptacle. The electronics unit (9) is configured to determine, from this reflection signal, a fluid level (11) in the shaft (2) or receptacle by way of time domain reflectometry.