Common Dolphin, Delphinus delphis - 37 miles per hour while riding ship's bow waves, 28 miles per hour in open water
That's while riding a ships bow waves, aka having fun. Wich is what they were doing when we saw them. At least for a couple minutes until they decided to leave us in the dust. It was only a small boat so I'm guessing the waves just weren't exciting enough for them. I'm guessing the sailfin and mako shark would still outrun them, but wouldn't tuna be one of thier food sources? Wich means they'd have to be fast enough to catch them.
Personally I think speed numbers on fish are probably a bit off anyway. Gotta figure how fast you run is directly related to what's chasing you.