It’s believed three men may have been snorkelling or fishing at Fingal Beach north of Cape Schanck when two of the men got into trouble just before 8am.
The other man managed to get back to shore and call police.
Search and Rescue, Air Wing, Surf Lifesaving, volunteer marine rescue units and local police are all assisting with the search.
Anyone with any information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au
