From what I've read about Ceph's and dolphins, it sort of sounds like a dolphin is like a dog, all playfull and friendly, and will even save your butt when you're in a jam, like Lassie.
But a ceph (an octopus in particular) is sort of like a cat, where maybe it likes you, but probably the only thing keeping it from wishing death upon you is an offering of food. And it will kill anything it can, for reasons that seem to be nothing short of "mean spirited." They take after Cthulhu.
There is one species on this planet that cannot be controlled by us, human beings: the shark. One can argue that rats, flies, cockroaches, mosquitoes, fleas (et al) also qualify for this category. To that, my reply is: have you ever heard of a shark exterminator? The point is: sharks have been around for a gazillion years before us; they will be here a gazillion years after we are extinct. Further, their domain is the sea; ours is not. WTF can we expect? It is their dominion. JMO.. a.f.