Here is a very short video clip to introduce the theme.
We did this coloring page of an x-ray fish.
The majority of our activities came from 1+1+1=1's X-Ray Fish printables.
My son really seems to enjoy cutting out the pictures of what we are talking about and gluing them onto the letter that corresponds like he did below.
We also worked on this hand print x-ray fish together. I painted his hand black and then he stamped it onto a white piece of paper. He helped me glue the little x-ray parts and the eye onto the hand print. Then he wrote the letter X in the left corner.