Absolutely! Greece is one of the safest countries to swim in. You will be glad to know that sharks in the Aegean Sea (usually from species such as dogfish) are harmless, sightings are extremely rare while attacks are unheard of! In addition, the waves are usually small, especially inside the Caldera where most boat cruises make stops for swimming. So, based on the above, if you enjoy swimming, snorkeling, or even diving... you are in the right place!