All you need is:
1 plastic zip top baggie per child (colored zips are nice to make sure they're closed tightly, but clear will also work)
a half-dollar sized squirt of blue gel toothpaste
permanant markers in a variety of colors
ocean themed stickers (optional)
In my case, we don't use blue gel toothpaste, so I went and bought a trial size. The only one I could find in blue gel had these tiny breath strip crystals, which actually turned out to look almost like bubbles.
Squirt your toothpaste inside the baggie, press out the air and seal. Then mush it all around with your hands so that it's fairly evenly distributed. This can be especially fun for the little ones. It's kind of like rolling out thin playdoh without any of the mess or clean up!
On my first attempt I used regular washable markers, which did not stick to the plastic. That's why I didn't post this project right away. I had to wait until I got some permanant ones. I would recommend that you do not use the extra fine tip, as those tend to just push the toothpaste around and not leave much color. These here are the regular fine tip Bic Mark It markers, and you can see that the color laid down very easily.
Then let the kids embellish to their hearts desire! In class, we did this project to coincide with the book "Commotion in the Ocean" by Giles Andreae and David Wojtowycz and an open discussion on sea life. You could do the same, or you could do this as a fun craft for an ocean-themed birthday party, or even just a boredom-buster on a rainy day.
In class, the teacher also allowed the kids to use stickers (though she encouraged them to draw as much as they could) but since I didn't have any, I just stuck with free hand drawings. It turned out pretty nifty, don't you think? I hope you'll enjoy doing this project with the little ones in your life!