Just got back from a 2 day trip to Legoland and went on the Atlantis ride.
See below for some thoughts.
** The following are my thoughts and mine alone if you don't agree sorry**
Atlantis if you didn't know is the new ride for Legoland and it is pretty neat ! (I don't mean clean)
We (Girlfriend and her two children 4 & 2) rode it twice once at the end of the first day and once about 16:30. They were different rides.
I'd read somewhere that its best to be sat down and that they were packing the riders in, luckily the first time there was 8 people inc us and the second about 10 so not to crowded.
Also i would say the Blue side gives a better View and ride experience and deffo try to sit with your back to the steps.
The ride itself is a little to short but i understand the huge undertaking that they have given themselves to maintain the Sea-life side of the ride so i can't grumble to much.
I can't really say anything negative about it the kids loved it and so did the adults, The theming is excellent and not OTT the outside Q will be bad in the rain but it moves reasonably quick.
After you exit is great for the kids and the shops not to bad or in your face.
Its a shame Legoland doesn't have walk-around characters i'd have loved to see the Atlantis Divers for some photo op.
On the whole a great ride, slightly short but a clever twist on the Sea-life concept