One of the most important parts of a swimming costume is the elastic. The elastic band keeps the swimming costume in the right shape and, more importantly, keeps the swimming costume from becoming loose and falling off. Unfortunately, the elastic is often the first part of a swimming costume to become worn out and to break. If your elastic band snaps, you may want to take the time to repair it rather than just throwing the suit out and buying a new one.
Turn your swim suit inside out. Use a seam-ripper to remove the thread from the seam holding the broken elastic in the swimming costume. Remove the broken elastic.
Pull the new elastic around your waist or bust, depending on the elastic you are replacing, to measure the proper length. Pull until it is slightly tight but still comfortable. Add about 1 inch to this length and cut the elastic with a pair of scissors.
Sew the two ends of the elastic band together using a sewing machine. Overlap 1 inch on each end of the band when you sew them together.
Place the new elastic inside the seam where you are replacing the elastic. Sew the seam closed using a sewing machine and thread.