Matthew Paris explains natural phenomena:
'Although other great and unheard-of wonders happened in this year , we have thought it worth our while to mention in this work one more remarkable than the rest. As it is the nature of the sea to vomit up on dry land the dead bodies thrown into it, about eleven whales, besides other marine monsters, were cast up on the seacoast of England, dead, as if they had been injured in some kind of struggle — not, however, by the attacks or skill of man. The sailors and old people, dwelling near the coast, who had seen the wonders of the deep when following their vocation in the vast waters, and trafficking to distant countries, declared that there had been an unusual battle amongst the fishes, beasts, and monsters of the deep, which by wounding and gnawing each other, had caused death to several; and those which had been killed had been cast ashore.
One of the fishes, a monster of prodigious size, made its way into the Thames, and with difficulty passed uninjured between the pillars of the bridge; it was carried as far as a manor of the king's called Mortlake, where it was followed by a number of sailors, and at length killed, after a great deal of trouble, by innumerable blows of spears. Of this event, a certain versifier jestingly remarked:
Venerat ad funus Thetidis de piscibus unus,
Quern rex Neptunus misit quasi nobile munos.'
[To Thetis' funeral came a monster fish.
By Neptune sent to make a glorious dish.]
These days it would probably be attributed to global warming.