Checked out Silverton Aquarium because it was FREE. Park by Bass Pro Shops and then it's closer to the Aquarium. They have a bunch of glass and you can sit or stand to see the aquarium. I wasn't able to see the Mermaid show or the Underwater Santa, just a bunch of fish.
Some mermaid art gallery next to it, meh and cheesy.
Only takes a few minutes to see them, but something to do when you don't want to spend money in Vegas.