http://www.captivakayaks.com/index.html Have been going to sanibel for a lot of years , never rented one of these but they look fun . I talked to them a couple of times and if I recall you are restricted to the bay side (pine island ) Sundail Resort used to rent a hobie type boat when we stayed there . If you want a bigger boat I think the closest place would be burnt store marina at charoltte harbor . There may be more but this is what I am aware of . Make sure you save one night to eat at the Timbers Restaurant . We have never had a bad meal or service there . We are heading down in a few weeks when the crowds die down .
We like Timbers but I judge restaurants by a strange standard of appetizers and dessert and Traders is my favorite. Even if you can't find a good place to rent a sailboat, the food on the island is excellent.
The food is excellent , water is warm , nice beachs. Just no decent place to rent a sailboat . Pretty much sums it up ,