The Black Lake was well known to have a mind of its own.  Any loch in Scotland might be in possession of a number of magical creatures, but the lake on the grounds of the Wizardry school was a law unto itself.  An abundance of grindylows, kelpies, and sprites lay in wait, eager to work their mischief.

 

But they were nothing to fear, to admire, to remark upon--nothing at all, compared to the selkies.