The Odra River boulevards
Boulevards are always a good choice to go to. Pedestrian zones on both sides of the river Oder are places of loads of small events such as "Bulwarove" or food truck festivals. Many people approach there to relax, chill and to admire the astonishing view of the Szczecin's waterfront. An unusuall experience that you might take a part in on the boulevards is a sort of aroma therapy, with a lovely smell of chocolate straight from the chocolate factory located nearby.
Obviously, it's also a good place to berth your boat there or go to one of plenty caffees and restaurants, that are always opened until nightfall. When it is hot, then you also should know, that there is an island between two banks of Oder, where a beach is located.