That's really too bad that you didn't have an awesome experience. I did the manatee trip with Gregory Sweeney in 2014 (http://www.gregorysw...rip_manatee.php) and thought it was fantastic. His trips are all about the photography and as such he keeps his group numbers small, and his itinerary flexible.
I did the trip in a drysuit and I was very happy that I did. We were lucky* that a very cold spell hit.
* Not so lucky for the manatees but the really cold weather was fortuitous in many ways: it drives the manatees into the warmer waters of the springs in large numbers, and the conditions are less hospitable for human visitors so most people don't find they can comfortably stay in the water long (which is good if you're in a drysuit and happy to hang out for people-free vistas).