I've been to Kusadasi and Izmir, Turkey close to the sea just last year in October if you check under pictures thread, You'll see some pictures that I've posted during my visited in Turkey, Kusadasi is like a beautiful painting with its blue clear water.
There are many activities and sightseeing to do in Turkey, such as to shopping bazaars, House of the Virgin Mary, the ancient site of Ephesus (the ruins of Ephesus), world famous Pamukkale, boat tour, the beaches and many more.
If you and your cousin are going together, it's best to stick together throughout the whole trip, never walk out alone or be alone, because you know those men in Turkey. I walked out the hotel once by myself, and just minutes later, some men start coming up to me so when you're with somebody, or a group, they'll leave you alone. So, just play it safe, you'll be fine.