I did the trip there via public transport and here’s how you get there. Once you know the station names, it’s quite straight-forward to get there directly from the airport:
1. From Amsterdam train stations (central, airport etc), take a service to ‘Harderwijk’, which is about a 70 minute train journey with one or two changeovers. About €15 each way, any route can be used.
2. At Harderwijk station, there is a bus station area right next to the tourist information building with about 8 different bays. Go to stop ‘G’ and take service 247 or 247a which says “Walibi” on the sign.
3. The times that depart in the morning to the park from this stop are the following:
9:22am, 9:52am, 10:22am and 10:52am for the first four. After that, it’s pretty much every 30 minutes all day. It’s €9 exactly for a return ticket.
This bus will take you directly to the park entrance plaza and the last bus back after park closure from memory was at 20:33 for the 8pm summer days.
Be aware that the bus is pretty packed, similar to the Thorpe ones and they only take card payments or a travel card similar to oysters (which is aimed more for the locals than tourists). Cash will not be accepted at all and yes, the buses do support Visa, MasterCard and Maestro contactless, including Revolut cards which was extremely handy in my case.
As for the trains, I would advise you to use their smartphone app called “NS Reisplanner Xtra” on either iOS or Android to book tickets and show the QR code to the conductor onboard when asked like I did. It is in English too this app so no translation problems.
I stayed at a hotel in Harderwijk for a couple of nights and from there, it’s pretty easy to get to the park, so the important bit is to make sure you reach Harderwijk bus station in all this.