UPDATE: Welcome to those finding this post in search of a parent/baby costume that is coordinated. I hope you try this idea because it is so easy to make. I did use a sewing machine, but you could easily hand stitch the teeth and lips on and sew the shark together. If you have any success or need some help, please don't hesitate to comment & I'll reply! Happy Halloween!!
I just had to do a recreate of this pin from pinterest.
Here is what I ended up with, and I think it turned out really cute! It is a great idea for a 3-6 month baby, that can wiggle a little, isn't too upset if they "lose" their feet, and cannot crawl. Bonus is that a parent can be "in" the costume with a lifeguard to the rescue!
4 hours ago