The passenger reportedly went overboard at 11.40pm on Friday during a voyage from Melbourne to Devonport, about 125km south of Melbourne.
AMSA Search and Rescue was advised at 12.10am and tasked two helicopters with night search capabilities overnight, including the Victoria Police Air Wing.
The Spirit of Tasmania II, along with two cargo ships, Sea Road Mersey and Victorian Reliance assisted Spirit of Tasmania I with the search this morning before continuing on their voyages about 8am.
Four helicopters and AMSA’s dedicated search and rescue plane from Melbourne searched a 247 square kilometre search area from first light this morning. Victoria Water Police continued to search the area until after lunch time.
The decision to suspend the search was based on expert medical advice that the man could not have survived past midday, taking into account various factors including water temperature and weather conditions.
Victoria Police are investigating, with the assistance of Tasmania Police.
Further enquiries should be directed to Victoria Police on 03 9247 5206.