Atlantis lines are like Disney lines: they peak during mid-day and are much smaller early and late. That being said, they never get as long as Disney. And Atlantis' setup is different...you don HAVE to wait in a line unless to want to go on that particular slide....you could just float along in your tube and take the conveyors all day.
The not-so-lazy river is the river system in Aquaventure. It consists of two main parts, the Current and the Rapids. the current is the wavy area where your tube is propelled along by 3-5 foot waves. Once your through that section, you hit a conveyor belt that you ride up to the top of the rapids. the Rapids are like white-water rafting, but in your tube. The whole trip through these two sections takes almost 40 minutes. And you can go round and round all day if you like.
At the top of that conveyor, there is a fork in the river where you can continue on the rapids, or take the fork and get on smaller river that will take you to the conveyor that get's you to the mid-level of the power tower, where you have the option of two water coaster slides (both similar to Crush & Gusher or Aquaduck). Note that to get to these slides, you haven't gotten out of your tube.
Which is the long way of explaining that yes, there can be lines, but some of them are well disguised because you never get out of your tube and you are not standing in the sun on concrete while waiting....you're in a tube in the water.
There's a bunch of other slides in the Power Tower and in the Mayan Temple, both body and tube, where you have to get out and wait like an ordinary water park. But once you've done those, you can get back in the river and just keep going round and round.
Atlantis has a lazy river, separate form its Aquaventure river. The truly Lazy River is by Atlantis' beach tower. It's like the lazy rivers at BB and TL, and I've never seen it crowded or with a line. It's actually a great place to go over to because it's delightfully quiet (few cruisers venture over there, though they are perfectly welcome to) and there's some great sea-life lagoon exhibits with turtles, rays, and sharks.
And then there are the beaches too. And the pools that don't have slides. And the Dig. And the tunnel aquarium.
Now, it can get quite crowded....particularly during busy times and when cruisers show up. But there's so many things to do that there's always something else you can do that avoids the crowds.
