Thanks everybody for all your helpful advice!
I just returned from my trip to Crystal River and unfortunately I'm a bit disappointed.
As written above any booking via email in advance was just not possible. I never got any answers from any of the tour operators despite some addtional telephone calls to them from some very friendly and helpful fellow wetpixel member.
Nevertheless I managed to book some tours directly in Crystal River at American Pro Divers.
This is what we booked:
1st day: Homosassa Springs tour at 6:30 am + Rainbow River tour at 1:00 pm
2nd day: renting a kayak and visiting Three Sisters Springs (not via American Pro Divers)
3rd day: Homosassa Springs tour at 6:30 am + Rainbow River tour at 1:00 pm
4th day: Crystal River tour at 8:30 am
5th day: Crystal River tour at 8:30 am
We had some bad luck with the weather. The weeks before we arrived it was very cold and hundreds of manatees were at the springs but when we arrived it was getting warmer and most of the manatees left the area for feeding. At Homosassa Springs we saw only 2 manatees, at Three Sisters Springs 3 and at Kings Spring (Crystal River tour) 2. But that can happen with nature and was not our biggest problem.
My main problem was that the groups were much too big for any kind of serious underwater photography. The boats had 16 seats and were always fully loaded with 16 people. Can you imagine what happens if 16 people try to chase and touch one manatee at the same time? In addition the water was very shallow and the ground was muddy. What happens when 16 tourists, inexperienced in swimming with fins, try to chase a manatee in shallow water with muddy ground? Right: visibility gets down to zero. Sometimes I was not even able to see my own hand in front of me.
Furthermore we were not the only boat there, not even at the 6:30 am tour at Homosassa Springs. At Three Sisters there were about 20 boats and about 200 people in the water. I was really trying hard but in these conditions it was just not possible to get any good images. We even canceled the Crystal River trip on our last day because it was just too frustrating.
I'm not really blaming American Pro Divers for this, the guides were friendly, competent and tried really hard to get the best out of this situation for everyone on the boat and all other tour operators had similar much too big group sizes.
If I would repeat this trip (which I won't do) I would not book any group tours at all, just rent a boat and get to the springs before sunrise and hope to get some shots before the first tour boats arrive. If you study some maps and talk to some experienced local people the manatees are easy to find by yourself. You therefore need no guide. And you should clearly avoid any visit around Christmas time
Maybe my above experience will help other people to get a more satisfying trip to the manatees.
Some more advice from my side:
- if you book a group tour all tour guides stricly forbid any kind of flash photography (fins were never a problem), as written on wetpixel there will soon be a new law which further restricts the use of flash even outside of group tours
- if you spend several hours in the water take the warmest wetsuit you have, I brought my 8mm one with an aditional 7mm hood and was happy to have it, my daughter was freezing in her 7mm suit (with 7mm hood)
- the Holiday Inn in Crystal River is ok and can be recommended
- getting good food in Crystal River is not easy, especially if you are a vegetarian like my daughter (you can choose between literally hundreds of burger shops, but that's it)
- Rainbow River is fun, not the greatest place on earth for underwater photography, but we really enjoyed it