The iPhone 6s Plus is not waterproof. Although it does have a level of water resistance, even a quick drop into water or excessive amounts of rain could damage the device. The resistance improves slightly with a case but by no means makes the iPhone 6s Plus waterproof.
Apple has noted that this resistance is not permanent and may decrease with time. So that means that on a refurbished or second hand phone the resistance might not be as strong. We like to say that some intense rain might be okay...the toilet, you might not be quite as lucky and we wouldn’t recommend swimming with your iPhone! 🌊🚫.
Always let your iPhone dry out completely before turning it on or trying to insert any cables. The old bowl of rice trick is known to work some magic. To remove any moisture form an iPhone's interior, a desiccant can help. (This is just a fancy way of saying a material that helps pull moisture out and maintain a state of dryness). Some people swear by putting a wet iPhone in an uncooked bowl of rice. So if it comes to that, you can give it a go 🍚.