I actually like slayer, I was thinking about farming because I don't know how to train it. As for my original post, I can probably bot some waterfiends..
It's just like a mini-game where you go around Runescape (once a time a week) finding 10 penguins. Once you find them all you can exchange the points for experience/money at the Ardougne Zoo.
Their's a thread on the forums where they update the locations of the penguins. It's actually really fun.