I don't like Snook Inn at all! I think it is ridiculously overpriced and the food isn't very good (just my opinion all you Snook lovers). For example, my daughter and I went last summer for lunch. We had tried it a couple of times before and not been impressed, but we were boating and thought it would be a great place for my husband to drop us off as we were getting hungry - thought we'd give it another try. Our lunches (not very good, I must say) and one strawberry daiquiri/one virgin daiquiri came to $70 . . . What a waste!!
Here are some other suggestions:
Marker 8 in Goodland (10 minutes from Marco) - Hole in the wall, but BEST food I've ever had. We go at least twice a week throughout the summer and have NEVER been remotely disappointed. Prices are reasonable and they will let you order off the lunch menu for dinner. GREAT people, great view and most of all GREAT FOOD!!
Pelican Bend in Isles of Capri (10 minutes from Marco) - GREAT food and a very nice view, as well. We do like Capri Fish House as another poster mentioned, but we prefer PB, which is right next door.
The Old Marco Lodge which was mentioned before is pretty good, too. My husband loves OML, but I think it's too expensive.
Hope this helps!