There's a lot that lurks below the surface of the Maribyrnong River and that's a problem when you're searching for body parts.

The river that sweeps through the north-western suburbs of Melbourne has collected a whole lot of rubbish over the years; witches hats, big old tree branches, beer cans, plastic, even the odd bicycle.

It's also collected a body or two, or, in the most recent case, body parts that have been floating to the surface since Thursday.

And it's all the rubbish below the surface that police must sort through as they continue to sweep the river's murky waters for the remains of a man whose identity was still a mystery on Saturday afternoon.