After you land to Athens you have the folowing two options: 1. Take another flight to Skiathos via https://en.aegeanair.com OR https://www.skyexpress.gr/en/ 2.Take a taxi to KTEL ( National Express for Greece ) o n the folowing link https://ktelvolou.gr/en/routes/map/&map=greece From there you will have the option to book your Bus and Ferry to Skiathos You have to Option to go from Mantoudi wich is much shorter trip to Skiathos . For more inforamtion check the link below https://www.ferriesingreece.com/destinations/ferry-to-mantoudi/