First things first, the trip and especially Captain Boyd were amazing.
He taught us about the keys, the bridges, the nature and landscape. We saw mangroves (white, black and red), birds (a few different egrets and herons, an osprey and many more), two sharks and lots of manatees (even a mother with her calf) and learned about them and the whole eco system as well as the history of the keys (especially Key Largo).
It was a pleasure going on this trip with Captain Boyd since he was very knowledgeable and cared about the environment and the wildlife. Unfortunately we saw no dolphins (not in the wild at least) but instead could catch a glimpse of four iguanas (three bigger orange ones as well as one smaller green one).
The trip on this small boat (6 passengers plus the skipper) took a little over 90min and it was worth every minute. At the end we got some vouchers for local restaurants which was nice. I can totally recommend this trip and if I come back to the keys I will definitely book this tour again!