Kea is actually even closer to the mainland than Kythnos, it just doesn’t always appear on the same ferry routes. If you are a licensed scuba diver or even remotely interested in snorkeling, Kea is is your place. There are some fantastic wrecks, and caverns, most notably the steamship Patris, which sank in the 1860s after hitting the island’s reef. That reef, by the way, means Kea is also rich in marine life. Sure, there’s good diving in Mykonos, but a dive is going to be, like, one afternoon of your trip tops, and then you’re stuck spending the rest of it with all the other people who go to Mykonos.