This image was inspired by an early Porcupine Tree song of the same name. The final 2 lines of the song go:
"On turning back, all I could see
Were her footprints on the sea"
So I blended it up!
I'm not sure if i still have this file anymore. It was done in late 2010, in the Blender Internal render engine (I think Cycles hadn't quite been announced at this point). It has a bit of composting/post processing done.
This is yet another project I hope to revisit in the future.
Cool!