While duct tape is the go-to material for fixing or patching just about anything in a pinch, it is not entirely waterproof. Most duct tape is water resistant, keeping moisture at bay for a short time, but eventually failing when wet. Some duct tape manufacturers offer waterproof duct tape, specifically designed for use in wet conditions.
Good for Repelling Moisture
You may have seen TV shows or videos featuring experiments in which duct tape patches a hole in a boat or is used to craft a complete makeshift canoe, tested on a body of water. Duct tape is a fabric-based tape with a polyethylene coating. Complete with a strong adhesive, this specialty tape repels water quite well, so it does hold up a bit when put to the test under water.
Check Labeling Regarding 'Waterproofing'
Over time, though, the adhesive may peel away from the object the tape adheres to, as the tape is water resistant, not waterproof. Manufacturers of duct tape offer a variety of duct-tape variations, including some designed to be decorative, featuring stripes or zebra prints, and others designed to be completely waterproof. While tape's adhesive and water-resistant qualities also vary from one brand to the next, if the tape packaging does not specifically state the tape is waterproof, it is not.