There is an excellent ferry that runs daily, weather permitting, to Portland and back.
The ferry boats are old wooden boats, one of which saw work witht he Americans stationed in Weymouth during the Second World War called My Girl.
Prices are reasonable and usually there’s no need to book but during peak summer time booking becomes more advisable.
The ferry to Portland leaves Weymouth near the Old Rooms Pub and drops you off near Portland Castle which is within easy walking distance of Portland Harbour’s new marina and the restaurant there called The Boat That Rocks. Beyond the new marina is the world famous Weymouth & Portland National Sailing Academy which will be home to the London 2012 Olympic Games Sailing Events.