I’ve not stayed at Turtle Beach, but have stayed at the place right next door 4 times in the last 2 years (Buena Vista, highly recommend for condo rental, but is not a dive resort). From what I’ve seen of TB, it’s a cool little place with lots of trees and shares an okay beach with BV and a few other properties. I looked into staying there a couple of years ago, chose BV because I wanted a deck with an ocean view, but would also be happy staying at TB. They feed some macaws which come screeching in a few times a day, really cool sight!
As far as diving goes, as mentioned above they used to have some kind of arrangement with Clearwater Dive Center; Clearwater has now moved about 1 to 2 minutes walk away (other side of BV) and have a little shop with their own pier. I have not dived with Clearwater but many of the guests at BV do and everyone I’ve talked to has been very happy with them.
Other things about that location in general: The beach sand is nice for strolling around but walking around in the water it can be a little silty or mucky. There is a cordoned-off section for swimming. Nice calm water for paddle boarding or kayaking. Easy 15 - 20 minute walk along the sand (and one large bridge of dubious stability) into West Bay. Can also walk to West End from there but it’s trickier, rockier, and has occasional bandit action so would not advise.
Have a great trip and please feel free to give me a shout if you have any other questions about staying in that area between WB and WE.