Weymouth harbour was shut down overnight on Saturday while bomb disposal experts checked to see whether the torpedo was still active.
Passengers sailing from the Channel Islands to Weymouth had to be transferred to Poole on Saturday night and passengers travelling from England to Guernsey, Jersey or France, were delayed for over two hours.
There was also a knock-on delay of around two hours yesterday .
The 15-ft weapon was found five miles off Portland on Saturday morning.
It was towed back to Weymouth, where the emergency services formed a 200m exclusion zone around the quay.
Royal Navy bomb disposal technicians analysed the torpedo and discovered that it had lost its warhead so there was no danger of it exploding.