I've found water clarity to be highly variable, even day to day. The good news is you will be there long enough that you will likely have at least a few excellent beach days. We visit the area in October, and out of the last few trips, we only had not so great beach conditions last year (red tide, lots of seaweed) for the majority of days. By November the water has cooled quite a bit so may be a bit chilly depending on when in Nov you go and what water temps you like. The average air temps though I find very pleasant there at that time of year, usually in the 70s. Still plenty warm on the beach. I would not heasitate to visit in November. Hurricane risk also drops significantly in November. Shell island is really fun and there is some really great snorkeling at St. Andrews State park which is kind of hard to find in the area, def worth a visit.
Although I find the beach conditions more variable there than in other places such as the Caribbean, the sand can't be beat by any beach anywhere, and it's much closer to get to from where I live. I figure a bad day at the beach is still better than a good day anywhere else!