During the warmer months, if travelling between the two sides of the city over the river wasn't already easy enough via bus, metro, tram and bike, there's also a free ferry service available Mon-Fri 12:30-19:30, Sat-Sun 09:30-20:00. In May, June and September, ferries run holidays and weekends only; in July and August they run daily. There are three short ferry routes, each with their own name:

'Wilga' - from the Vistulan Boulevards in front of the Multimedia Fountain to Rusałka Beach in Praga.
'Pliszka' - Poniatowski Bridge on the left-bank to the Poniatówka Beach in front of the National Stadium.
'Słonka' - from the floating pier at Cypel Czerniakowski to Saska Kępa Beach.

All ferries can take 21 people and 21 bikes with the exception of 'Wilga,' which can take 40 people and 40 bikes.