Highly recommend making time to visit Klein if you have a free day in Curacao. The island is uninhabited so quite deserted. If you go on a day that Mermaid Tours doesn't have a planned tour, you will nearly have the island to yourself. Do take water shoes, which you will also be glad to have if you choose to explore the island. There is a very rocky shoreline that isn't immediately visible to the eye, so it may deceive you. Also be sure to take snorkeling equipment or borrow some from your tour group. It's a bit pricey, but definitely worth making the visit, especially since breakfast, lunch, and an open bar are included! See my review under Bounty Adventures Tour for more details.