Originally got this idea from the fabulous Use Your Coloured Pencils blog (see link on my homepage). I've altered it slightly and just completed it with a group of Year 2/3's. After an initial panic that they wouldn't be able to draw the swimmer, they absolutely loved it!
On the first day, we created our marbled paper to use for the water and printed ‘bubbles’ on our background paper (using plastic lids and acrylic paint). The next two lessons were taken up with drawing and colouring the swimmer and painting little white reflections onto our ‘bubbles’. The final session involved cutting out the swimmer and assembling all the layers. The kids (and I!), were really proud of the final artworks.