Public transport is certainly the most viable option for tourists without their own wheels however, and despite being outside of city limits, Kraków's public transport system will still get you there. Take any tram which terminates at the 'Salwator' tram roundabout, and from there you can catch bus 209 to the 'Budzyń Zalew na Piaskach' stop, right across from the Skansen Smaków restaurant. Or, take bus 269 from Salwator to the 'Budzyń Plaża Główna' bus stop, right near the main entrance to Kryspinów's guarded swimming area. The journey only takes 15-20mins and both stops are within walking distance of each other, so they're equally good options. Note that both Kryspinów bus stops are 'requested stops' (meaning you need to press the stop button on the bus to let the driver know you intend to get off there), and that for both you'll need to buy a 4/2zł fare that is valid for both Zones 1 and 2.