You meant to the theme park? Yes, if you plan to get wet at several water play facilities. Recommend crocs too.
The hotel provides towels but the theme park does not.
Yes, bring your own towels if you're going into the waterpark or pool area. As mentioned before, you can get towels from the hotel if you're a guest there, but if you're just visiting/walking around other parts of Legoland there are a few separate water related activities that typically could get you wet enough to cool you off a bit and then dry off as you walk around so in our opinion no towel needed for non-pool/waterpark areas. For non-pool/waterpark area think waterguns, which if you don't move could theoretically spray you for up 8-10 seconds non-stop or a splash of water here and there.
Splash battle and pirate reef too you get soaked
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