We saw the boat trips when looking over Wawel Castle walls.. Walk down the steps and you are greeted by the 'sellers'... No hard sale and for a lovely 30 minute trip along the Wisla River was 25 zloty.. About £5. Small boat of maximum 12 passengers, no commentary, but sometimes it is nice to just enjoy the view. Would definitely recommend. A short walk from the boat is the fire breathing dragon statue.