On spatterdock leaves. There were also larvae on the leaves which looked to me like waterlily beetle larvae, but the only adult I could see with these larvae was this adult beetle. It did not seem to want to fly off, if it could. I plucked it off the leaf and it didn't fly away.
Huge! On Nuohar advena
Ochlockonee River State park, on Sparganium lancifolium
First iNat obs for this species