The "Chef's Thunder" can, and frequently does, change daily, so it may not be flounder on the day you go. That said, it's what I usually have when I'm ordering off the regular menu (as opposed to at one of their special events), and it's always been excellent. I was most surprised by the day boat (which is to say, from ocean to plate in under 24 hours and never frozen) mahi mahi. When the server suggested it, I half-seriously asked what I'd done that he'd insult me that way. In Florida, mahi is usually a tasteless, junk fish for tourist traps. He offered to replace the chef's thunder if I ordered it and didn't like it. I didn't have to take him up on it as it was excellent.
If that day's special doesn't appeal to you, the scallops over risotto have been consistently good also.