I just got back from 10 days in Sanibel. (7/20/05 - 7/30/05)
When we first crossed the bridge to the island, we noticed the normally pristine, aqua-blue colored water looked more like dark river water. When we got to our condo on Middle Island beach, we noticed the water on the beach was actually a tannic brown color and smelled like sulfur.
We found out the Army Corp of Engineers is draining Lake Okeechobee into the Caloosahatchee River which drains into the bay at Sanibel. It was horrible. The locals told me the Okeechobee is overflowing and they had no choice in the matter. This Lake Okeechobee drainage could last for at least a year depending on rainfall.
The accomodations were nice and the restaurants were great, but it is a horrible place for a beach vacation.
I only wish someone would have warned me before I booked my vacation.