Natural yarns are not water-resistant nor waterproof. But synthetic and blend yarns are most of the time water-resistant because of the polymer. If you want to waterproof your yarns for your projects, it’s easy. Waxing You can use paraffin or beeswax for this process. Before you start your crochet project, it’s better to wax your yarns first. You can start with a few meters and just continue waxing as you go on with your project. Waxing is simple. Get a chuck of paraffin or beeswax and run it over your thread. Make sure that the wax covers the entire yarn by pressing it with your thumb as you pull the thread. Waterproof Sprays Another option is by using waterproofing and seam sealant sprays. You spray any of these chemicals on to your finished projects. You can buy them in crafts stores, textile shops, and online stores. When you apply these chemicals to your finished projects, make sure you do it in an open area. This will prevent the chemicals to linger around your home or other home furnishings. Spray these chemicals on both sides of your swimsuit. Let it dry before using them. It will be best if your swimwear can fully absorb the waterproofing chemicals. Let it sit for at least 24 hours.