The Siren is a painting by John William Waterhouse. The painting depicts a siren sitting at the edge of a cliff, lyre in hand, staring down at a shipwrecked sailor floating in water, who in turn is staring up at her. The picture was painted in 1900 and is now part of a private collection.
I love this rendition - the finns at her legs are just subtle enough that he would not have seen them when jumping off the boat, but enough that he's just about now realising that something is seriously wrong.
In most media with sirens I've seen they turn monstrous before they feed. I've always felt like it would be much more disturbing if they didn't. This gives me some of those vibes. Awesome painting.
Yeah I picture it looking like cannibalism with a disturbing amount of glee. Personally I find the idea of this nearly human creature happily devouring flesh to be quite creepy.