Coming from the main exit/entrance of Amsterdam Central Station:
Turn left and walk towards the tramplatform. A little bit further, you will see the newly built HILTON/DOUBLE TREE hotel. Walking along the HILTON/DOUBLE TREE hotel you will see a bridge. Walk towards the bridge, cross it and you will see The Beagle.
Enter ''Beagle Houseboat' in maps.google.com to find its exact location.