The handle of a folding knife can vary depending on the materials used. While some handle materials may be more resistant to water and moisture, it is important to note that most folding knife handles are not entirely waterproof. Common handle materials such as wood, bone, and certain types of plastic or composite materials can absorb water or be damaged by prolonged exposure to moisture. This can cause swelling, warping, or other forms of damage to the handle.However, there are some handle materials like certain types of synthetic polymers or G10 (a fiberglass-based laminate) that are more resistant to water and moisture. These materials are less prone to swelling or warping and can handle exposure to water better than others.That being said, it is always recommended to keep your folding knife handle as dry as possible to prevent any potential damage. If your knife does become wet, make sure to dry it thoroughly before storing it to minimize the risk of damage to the handle or other components.