How To | Shark Boy Costume

My tutorial for a Lava Girl Costume has been very popular. My sister made a Shark Boy costume for her son last year and I thought some of you would like to see what she did and make your own. (If you are looking for Lava Girl costume instructions go here.)

Since I did not make this costume myself, there are no step-by-step pictures. This costume doesn’t require any sewing though and would be easy for anyone to make.

How To | Shark Boy Costume


  • Gray Vinyl
  • White or Darker Gray Vinyl
  • Fabric Chalk
  • Cardboard
  • Craft Glue
  • Duct Tape
  • Scissors
  • Black Sharpie Marker
  • Adhesive Velcro

How To:


  1. Get out a shirt of the child you are making the costume for. Use the shirt as a template to draw out the shape and size of the shark “shirt” on the vinyl. My sister made the vinyl shirt so that it would slip over her son’s head and then velcro at the sides near his waist. See the picture of it below.
  2. Once the vinyl shirt shape is drawn, cut it out. Use a black Sharpie marker to add detail to the vinyl shirt. (Here is a link to a picture of Shark Boy from the movie.)
  3. Cut out the shark mouth shape from white or darker gray vinyl. Glue the shark mouth in place. Let dry.
  4. For the fin on the back of the shirt, cut a large triangle out of cardboard. Cover the triangle of cardboard with duct tape. Cut a slit the width of your shark fin in the back of your vinyl shirt. Use duct tape to tape the fin to the vinyl shirt. The tape will go through the slit and be hidden inside the shirt.
  5. Have your child put the vinyl shirt on and then add the velcro to the sides of the shirt.

ARM FINS – The arm fins are created using mostly duct tape and then cardboard for the fin part.

  1. Measure the length of your child’s arm from his wrist to below his elbow.
  2. Cut out four cardboard fins, two for each arm. Cover the fins with duct tape.
  3. Use the measurement you took of your child’s arm to cut your duct tape strips. Create a wide, bottom layer of duct tape strips, sticky side up. When you get the bottom layer the width you want, use more duct tape to create a top layer that covers the sticky side. As you add the top layer, tape your fins on too.
  4. When the fins are the right width and fit all the way around your child’s arm add sticky velcro. Be sure to account for what shirt he will be wearing underneath the arm fins so that the arm guards are big enough to fit over the sleeves.


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  1. I was wondering if the costume would look okay being made with a different material? Vinyl is really expensive. And if so what other material would you recommend?

    • Hi,
      I think you could really use anything that is gray in color. If you have a Jo-Ann’s store nearby they have some vinyl and you can use a 50% off coupon… Good luck. I would love to see your finished costume!

  2. How do i post a picture? I follow ed your directions and it turned out great! My daughter wants me to post her picture it was a huge hit !

  3. Hello, my son is wanting to be shark boy for Halloween this year.I wanted to see if you had a pattern you could share. I would love to make this for my son.