Hi,
We visited Weeki Wachee Springs on our last visit and thought that it was really nice. We didn't spend the whole day there but we spent about 4-5 hours.
The Bucaneer Bay and Scuba Diving was fantastic - a real highlight from our trip. There is also some fun flumes and rapids too, which everybody enjoyed. It is really nice swimming in a natural spring rather than a man made pool, and I thought that the facilities were great. Unfortunately we didn't go canoeing as it was fully booked, but this is definitely something we will try when we next visit there - just make sure you book well in advance. The 30 minute snorkelling tour is great fun and even the children enjoyed it - the scenery was lovely: The manatees are beautiful.
The 'world famous' mermaid show the children enjoyed, but i'm not too sure about the adults!
A whole day here can work out quite expensive but it is really enjoyable and never felt crowded.
Richard.