Great you all met and had an adventure!!
I've been doing manatee the last couple of days and yes the viz has been variable. It is because of weather fronts and conditions. But sites can still clear and as was stated it can be good because you just shoot close and nothing else in your pics!! 
Still there are lots of manatee and Crystal River and it has been just gorgeous out, the sun returned!!
I did get a chance to take down my new Tokina 10-17 lens today. It was awesome and the Subal lens gear worked flawlessly. I still like my nikon 16mm and am glad I used it so much and learned to get a lot out of it but I love shooting manatee with the wider lens - what a treat!, and now I'll be able to get shots I haven't been able to before - more variety in my manatee photo collection....
OK, got to close tired now, it will be cold and clear again tomorrow. Let's just hope the viz clears...... As I've previously stated you don't need to take up any extra sources of gambling when you bank on shooting manatee and try to figure out the clarity of the springs at Crystal River! But manatee are lovely and mesmerizing in any light and viz I'd say....
Best Carol