Really? I just watched it again and don't see any. What time in the video are you talking about? Those are black tips, dolphin in the Gulf are usually pretty damn big. I didn't see any horizontal tails either, but then my eyes are starting to suck. A visit to the range back in Dec told me it's time to get my script tweaked. Booo.
Dolphin will tail tuna, join in, get right in there with them, but I'm pretty sure they understand being in white water with a couple hundred feeding sharks means someone's getting bit.