LOTS of stuff to do in St. Augustine. I liked the alligator farm. World golf hall of fame is there. I used to live in Jacksonville. If you are bored in st. Augustine, you must be trying very hard to be bored. Love that area. I'm sure you will have no problem finding something to do. Although, I found it weird that that area has no major aquarium. There's marineland, that is a dolphin "oceanium," and Jacksonville has a zoo and gardens. just depends on what you are into.
Look for a spring fed river to canoe down. There aren't many close to St. Augustine so a drive is required. If you're into plants, that's something you shouldn't miss. You'll see many of the plants you keep growing in the wild. I used to live near Gainesville which is surrounded by springs. It hasn't gotten old even after nearly 50 years of seeing them. Try to take a mask and fins. You'll want to get in and see things close up.