Dark appreciated the merman, partially because he was not himself a buoyant man, and it was impressive to see someone else float around so effortlessly. Just like the mermaids, though, he didn't have any strong feelings about it. The merman was clearly closer in age to his children than he was to him.
After the final, admittedly quite impressive, tricks concluded, the performers swam to the top for another breath of air and then swam down to the glass so people could wave hello and have their pictures taken with them. Since they knew there was such a crowd and they couldn't stay underwater indefinitely, they all were at a different spot near the glass so there could be three separate queues.
"Did you like that, Ivy?" Dark asked, standing up and walking over to his sons. Seeing the look on Alec's face, he wordlessly tapped him on the arm to subtly suggest he pull himself back together without calling any attention to it or (hopefully) causing embarrassment. "That was interesting, I did not expect that."