LONDON -- There's a reason you never catch Dementors in water, and it's not because they don't like getting their cloaks wet.。

The real reason is obvious: there are far too many magical fish out there that would blast them into oblivion with their tiny, adorable patronuses. 。

Just look at this one in action:。

Thanks for signing up!。

Tweet may have been deleted 。

OK, so it's probably worth mentioning at this point that fish can't really cast Patronuses (at least not that us muggles know about, anyway). 。 The little cardinal fish in the 。BBC Earth。

clip above -- which went viral after it was shared recently on Twitter -- is actually regurgitating a creature called an ostracod, which gives off that bright blue light when swallowed as a form of defence.。 Then again, who knows?Then again, who knows? Maybe that's what they just 。