This card is a nod towards rainbows, by way of rainbow fish!!
It is a Z-Fold Pop Up made from dark blue mirrored card.
The bottom band is cut in a wavy line along the top (to represent the sea floor), from a piece of blue and green patterned paper from the First Edition 8 x 8 inch Wild Flower paper pad.
The fish are die cut, coloured with paint, then glued via acetate strips to the box section and back of the card.
The other embellishments are stickers and stick-on gems from stash.
There are several youtube video tutorials available online on how to make a Z-fold popup card, if you wanted to make one similar.