I thought I'd try some bubbles in an underwater scene... I used Memento Luxe for the white ink, and black Memento for the shading. In hindsight I wish I'd used a color that matched the cardstock - so keep that in mind if you use a base color other than black.
I stamped the mermaid on the card base so I would have the details in place, then stamped her on ivory cardstock to color and fussy cut. Also... is that teeny jellyfish not the cutest thing ever...?
I stamped some more 'bubbles' (they're supposed to be water or oil droplets, but why not?) and then added some drops of hot glue for more dimension.
Stamps I used: Splash, Water Waves, Bitty Blocks - Cool, Drops