You can sail around the entire island of Capri (without stopping) in an hour, but most boat companies offer tours of 2 or 4 hours or for the full day.
A two-hour tour is perfect for those visiting the island for one day who also want to see the island by land. A full-day tour is best for those who want to stop for lunch at a waterfront restaurant or take time to swim, but can be tiring for those who are not used to being out on the water. The ideal tour is a four hour trip, which includes enough time to sail around the island, visit the sea caves, and stop for a swim.