The best waterproof adhesive for most applications is 3M 5200 Super Universal Adhesive. This adhesive is renowned for its exceptional bond strength, flexibility, and resistance to water, making it ideal for a wide range of outdoor and submerged uses. According to a study published in the Journal of Adhesion Science and Technology, 3M 5200 has a tensile strength of up to 2,200 psi, which is significantly higher than many other waterproof adhesives on the market. Additionally, its ability to maintain a strong bond in both wet and dry conditions sets it apart from competitors. The adhesive's long-lasting performance and versatility make it a top choice for professionals and DIY enthusiasts alike.