Hey Ben,
Yes I have been to Shark Reef at Mandalay Bay n Las Vegas. I was skeptical of it at first, but was pleasantly surprised. Tickets are $18.00 for adults. You start out the tour at your own pace self guided. The entrance is like you are on a tropical island and eventually work into and under the water. Each exhibit has a placard along with a button that you push to hear other fact about it. You are given a handheld speaker-phone thing that works with the push button. Lake Mead is open for divers and its main attraction is a WWII B29 bomber that soft landed on the water and sunk intact. However, it is accessible only by tech divers due to its depth. Let me know if this helps you out and how the Shark Reef is for you. Hope you enjoy.
Curtis