Aussie swimmer killed by jet ski

A 51-year-old swimmer has died in hospital after he was hit by a jet ski.

Police believe the man was swimming in the water around Lagoon Pier at Port Melbourne beach at 5.50pm (local time) Friday when he was hit.

He died in hospital on Sunday morning from severe head injuries.

Witnesses have told police two men riding on a jet ski collided with the swimmer.

Emergency services were called to the scene and the South Melbourne man was taken to The Alfred in a critical condition.

The driver of the jet-ski, a 21-year-old Roxburgh Park man, has been assisting police and was released pending further enquires.

-AAP