I was at the water parks in
2015
Saturday and Sunday before Labor Day
Saturday of Labor Day Weekend - more crowded than previous weekend
Tuesday after Labor Day - least crowded
2016
Saturday and Sunday before Labor Day
Saturday of Labor Day Weekend, - more crowded than previous weekend
Labor Day. - least crowded
Saturdays more crowed than Sunday
The first consideration is, what are your other options?
For me, the other options were:
1. stay in at my resort and hang out
2. switch water park days and one of the 4 parks days
Were the water parks noticeably more crowed on Labor Day (Saturday)? Yes, but it wasn't insane. Just longer lines.
Are the water parks a better option than the regular parks? ABSOLUTELY!!!! I would much rather go to the water park on a slightly more crowded day and save the less crowded day for the regular parks. Furthermore, I know lots of people claim that the 4 parks are not crowded on Labor Weekend. Now, in the last ten years, I've only visited around Labor Day weekend, so I can only compare it to that time frame. The parks on Saturday and Sunday of Labor Day weekend are significantly more crowded that the days before and after the weekend. So much so, that I now use at least 2 of the Labor Day weekend days as water park days. I am sure the parks are less crowded than all other holiday weekends, but they are by no means empty.
Are the water parks on this weekend a better option than hanging at the resort? To me, yes. The resort was a zoo and otherwise, I'd be wasting a ticket.
If I could pick from all the days of the year, would I pick a different day to visit the water parks? Yes...for example, the Tuesday after Labor Day was great.
Just like any other park, if you are concerned about long lines, get there early and do the headliners first. Use the afternoon to lounge, laze in the River, wade in the pool, snack and have a drink. Lines will drop again as the day progresses. If it rains, strangely, the park starts to empty. It's great then.