I haven't been there before but am planning a future visit. In the picture it looks like water on both sides of the beach area. Am I seeing it correctly?
That is the inlet (sometimes called the outflow) of Western Lake, in Grayton Beach. All the lakes have something similar: a channel of water connecting them, sometimes, to the Gulf. You will like it.
We love being in SoWal mid-late August. Ocean and pool like bathwater, no crowds yet all the benefits of SoWal. This will be the first year we'll spend more time in SoWal in Jan/Feb. It won't be as warm, but it will be a LOT warmer than Michigan.