Sorry... I was stuck out in Texas last year during August.
But generally if the park is open till 10pm... I wouldn't head out there till about 2-3pm.
A) it'll help save you from getting sun burned because the worst of the day over.
B) crowds are leaving because they got there first thing in the morning, and burnt crisp
C) easier to find chairs
D) you can have a decent lunch else where, and not pay the price of food there. Unlike Sea World, the food at Aquatica isn't impressive at all, and just as expensive
E) you'll feel like you have the whole park to yourself at night. And here, it's just as hot at night as it is during the day.