Pliny the Elder

Natural History 9.8

…In the days of Augustus Cæsar the Emperor, there was a dolphin entered the gulf or pool Lucrinus. This dolphin loved wondrous well a certain boy, a poor man’s son who went every day to school from Baianum to Puteoli. This boy was wont also about noon tide to stay at the water side and to call unto the dolphin, Simo, Simo, and many times would give him fragments of bread, which of purpose he ever brought with him, and by this mean allured the dolphin to come ordinarily unto him at his call. I would make scruple and bash to insert this tale in my story and to tell it out, but that Mecænas Fabianus, Flavius Alfius, and many others have set it down for a truth in their Chronicles. Well, in process of time, at what hour soever of the day, this boy lured for him and called Simo, were the dolphin never so close hidden in any secret and blind corner, out he would and come abroad, yea and come up to this lad, and taking bread and other victuals at his hand, would gently offer him his back to mount upon, and then down went the sharp pointed prick of his fins, which he would put up as it were within a sheath for fear of hurting the boy. Thus when he had him once on his back, he would carry him over the broad arm of the sea as far as Puteoli to school, and in like manner convey him back again home, and thus he continued for many years together, so long as the child lived. But when the boy was fallen sick and dead, yet the dolphin gave not over his haunt, but usually came to the wanted place, and missing the lad, seemed to be heavy and mourn again, until for very grief and sorrow (as it is doubtless to be presumed) he also was found dead upon the shore.