Try their web site,
www.showboat.nl
Take the train to station Zaandam (
www.ns.nl for time schedule )
Transfer to bus 88 in front of the station
Ask the driver for bus stop Koperslagerstraat
The Showboat is moored on the right-hand side after 75 meters
or take a taxi from the Station in Zaandam
Or from Station, it is a 10-15 minute walk. When you come out of the station, turn right and walk along the main road. About 1.5 miles down, the road bends towards the right and after a few yards, you will see the Showboat on your left hand side.
Hope that helps.