The external pocket of the Rapid or Flow Dry Pack is water-resistant, but not completely waterproof. The zipper is designed to be water-resistant and can withstand light rain, but it may not keep out water during heavy downpours. Additionally, while the seam that attaches the pocket to the body of the pack is taped on the inside of the main pack compartment, it cannot be taped inside the pocket. As a result, water may eventually seep through the seam into the pocket.
For this reason, we recommend that you use dry sacks to store any sensitive items you want to protect from water, even if you are using the external pocket of the pack. The main compartment of the pack is designed to be waterproof, so using dry sacks will ensure that your items stay completely dry.