We stayed at Mandalay Bay during our visit to Vegas. We are bug aquarium lovers so were excited to check this out. I would definitely say it is underwhelming. The first few areas almost seem a little sad. There are a couple OK tanks, with some cool fish, but in no way would I call it a "Shark Reef". There really aren't that many sharks. I would say it is not worth the $20. Go spend it at the casinos!