Berlin, although a landlocked city, has a great beach area on the outskirts of the city. The Strandbad Wannsee area is very family friendly with full washrooms and change rooms. It also neighbours a marina with plenty of boating options, including sailing. From central Berlin, it is about 30 minutes by train and another 15 minutes of walking (from the station to the beach area). Access to the beach area is roughly €5.50 depending on your age and student status.