Transforming a person into a dolphin is a somewhat tricky process. A dolphin is all one shape, while a person has several limbs that make it difficult to convert into a dolphin shape. You can create a suit that looks like the body of a dolphin from craft foam. The person can then wear the costume like a jacket to transform themselves into a dolphin. This project will take about two or three days to complete.
Draw the outline of a dolphin body onto a piece of butcher paper. Make the outline long enough to cover the person who will wear the costume from over the head down to the ankles. Make the outline look like the side profile of a dolphin with a pointed top for the head.
Cut out the paper. Transfer the pattern onto a piece of flexible craft foam. Cut out two outlines. Glue the two shapes together along the long back edge where the patterns match. Allow the glue to dry overnight.
Cut two flipper patterns from the craft foam long enough to cover the costume-wearer's arms. Cut a hole in the sides of the main body of the dolphin large enough for the person to slip their arms through. Glue the dolphin fins to the top of the holes in the dolphin body.
Cut a tail shape from the foam. Glue the tail shape to the bottom of the costume. Glue the dorsal fin to the back of the costume. Allow all glue to dry overnight.
Have the person put on the costume. They should slip their hands through the holes in the main body of the costume and the flippers should cover their arms.
Attach one or two strings to the costume to hold it in place along the body. Use scissors to punch a hole in the costume so you can tie the string in place.
Paint the costume blue or grey and have the person wearing the costume wear a white sweat suit to mimic the belly of the dolphin. Add eyes and other details to the costume to make it realistic.