I lived there for a while...
...And Steven is right- The southern end of the bay is pretty shallow. There are more places to launch from than Destin harbor- I can help you find a place to launch your boat that will keep you out of the way of the barges and fishing boats. My personal favorite public launching spot was Liza Jackson state park, right on Hwy 98 in Fort Walton Beach. It's a bit of a sail through Santa Rosa Sound to the open waters of the bay, but the ramp, docks, and parking areas are all well kept (and also $free). I can also recommend a few neat little places on Choctawhatchee Bay for dining or overnight anchoring. Let me know if you're interested...--Jon BastienH25 'Adagio'jonbastien(at)yahoo.com