score:7
They are allowed. They even sell them in the shop there:
They are! And they sell them in one of their shops if you don’t have your own. They even have a pump in the same shop to blow them up if you want. I’m sure you could use it to blow your own inflatables up too but I don’t know. Prices are very reasonable! I got a giant pineapple (can fit 2 on) for about €30
(Source: TripAdvisor)
Also confirmed by emailing them:
Inflatables are allowed. The usage might be restricted depending on the life guards and the number of guests in the water.