The Alachua Sink behind Sonny's is formally known as Mill Creek Sink. The property is owned by the NSS but managed by a guide system. It's a beautiful system when it's clear, but frequently the run-off from Mill Creek leaves visibility minimal in the basin and cavern zone. It's also deeper than recreational dive profiles. Due to the depths and an unfortunate fatality in 1993, it is a guided system only - I became a guide in January but have only been able to take two groups because it's been blown out since February. Pre-reqs to dive there are full cave + 100 post-full cave training cave dives, trimix certification, and being a member of both the NSS and the CDS.
The Alachua Sink off the La Chua Trail in Paynes Prairie is a different beast. In addition to being full of alligators, it is a siphon, pulling water in from PP into the aquifer. The only two people I know that have ever been in there include Tom Morris and Wes Skiles, but it's possible Pete Butt has too. I may see Pete on Saturday and can ask him.