"They're very similar," Duke said with a nod. "A lot of people can't tell them apart, especially from this distance. But look at the fin: see how it's small and pretty triangular? Dolphins have taller, curved fins. Their faces are pretty different, too, but you'll only see those if they --"

Fandom being what it was, and the Cape Rouge being very close to Fandom, one of the porpoises obliged Duke by leaping all the way up out of the water. Duke beamed.

"-- Do that."