Hi Marlin,
In Crystal River I always recommend American Pro Diving on SR-19. They run a first class operation. Sean Bradley is their course director--tell him "hi" for me (we worked on a liveaboard together in the Bahamas for many years) and he will take great care of you. Be aware that manatee season is during winter months--you will see a some manatees but not the large congregations you will see in Jan./Feb. also be aware that most operators do not allow diving with manatees, only snorkeling (it is a violation of Florida Freshwater Game and Fish laws).
Blue Grotto is a lot of fun, as is Devil's Den right across the street. Both have decent rental gear so I would probably rent it from them (it's easier).
If you happen to be in The Villages the first Wednesday in August we have our monthly scuba club meeting at the Laurel Manner Rec Center at 7:00 PM. You can meet our members and we usually have excellent guest speakers/presentations. You can also check out our club Facebook page (
https://www.facebook.com/groups/272268682854434/) and maybe find some additional dive buddies.
Let me know if you have any further questions,
Jon
Let me know if you have any questions.