We booked this excursion just so we could get out to Oia a quickly as possible and still have time left over to visit Thira. The excursion was nothing more than a $50 bus ride from the port where the tender dropped us off out to Oia, featuring the ramblings of a local tour guide. 2 hours of free time in Oia to explore, and then back on the bus to Thira where the excursion ended. The value of the excursion is in the time saved by having direct transport rather than the lost time of tendering to shore, hiking or taking the cable car up to Thira, and then searching for a cab to Oia and back. Overall, visiting Santorini on a cruise is not the best way to see the island based on a previous trip dedicated to the island. There are too many cruisers in town (up to 5 ships worth at once), and most are crammed into the two small shopping areas in Thira in Oia, which is not very pleasant. Recommend finding a cruise that allows the time to explore the non-cruise areas (ex: beaches, ancient ruins, wineries, etc), or to just make a dedicated visit to the island...it's worth it!
Read cmpuyot's full Westerdam cruise review
Holland America Line