I spent a day in Mull, got the Ferry in Oban, arrived at 11am in Mull, spent 1 hour at Duart Castle (much better outside than inside but is worth the visit) and headed to Calgary Bay. From Duart Castle, take the road to Tobermory but leave the main road at Salen and take the B8035 and then B8073 all the way up to Calgary Bay. The scenery is stunning! Getting to the bay from the B8073 you will have an amazing view over the beach, park the car and enjoy the beach, it is absolutely beautiful! I spent an hour there and headed up to Tobermory before getting back to the last ferry in Craignure at 7pm. An amazing day trip!