Amazing valley near Muscat that you can walk through. If you've rented a car, you can easily drive up to the entrance and then hike through the Wadi. If you don't have a car, any hotel can help you book a tour with a private driver (although they can be expensive 120-160 OMR for a car that holds up to four people).
If I did this again, I would spend the full day here. Bring lunch, hike in a bit and then go for a quick swim. A lot of the tours will take you to Sur and to swim in the sink hole but I would recommend more time at the Wadi and skip the other stuff.
It's about a two hour drive from Muscat.
Definitely worth doing some off roading on the way there / back from Muscat. There is beautiful scenery through the mountains. You may need to have a guide to find your way through these though as they are primative dirt roads with no road signs.
If you own or manage Wadi Shab, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.