The fabric I've used here is some I dug out of a pile I bought ages ago - the beautiful mermaids are an organic print from Birch fabrics, and the solid blue is a Kaffe Fassett (no idea what the colour's called) that matches the mermaid's tail exactly.
On the back I've used another part of the print, with some wading birds feeding on a sand bar. I really, really like this fabric - it's quirky but reflects nature (...cos do mermaids exist or not? What do you think?).
I've used an invisible zip here, but not sewn it in "invisibly". I just like the neat look when it's closed, and the little tiny zip pull. If you don't know Noodlehead's blog, do have a look (Noodlehead), she has a great selection of tutorials with clear instructions. If you try this pouch, make sure you buy a plenty long enough zip for the size you're making, as it makes all the difference being able to pull the zip right past the end of the pouch.