You can take your bike with you for free from Ikaria to Piraeus, if you travel on large ships such as those from the company Blue Star Ferries. However, on ships without a garage, bicycles are normally not allowed inside. You'll see if the ship has a garage when making your reservation. Ikaria can be busy in the summer so it is a good idea to tell a member of the port staff that you have a bike in case you might need extra assistance.