The 85-year-old's wife alerted police after he did not return from a swim off the beach in the town of Marina di Campo, Ansa reported.
One of the police officers saw the man floating in the sea, and swam to try and save him, with the help of two other swimmers.
Emergency volunteers tried to resuscitate him, but he was prounounced dead at the scene.
Earlier this month, two British tourists also died while swimming off the coast of Lloret de Mar on Spain's Costa Brava.
Lisa Coggins and Tracey Aston, from Birmingham, were swept away in rough seas after going swimming in the early hours of the morning.