OverBoard Classic Waterproof Backpack (30 Liters) Black. The black, 30 liter Classic Waterproof Backpack from OverBoard is a bag with a 1,800 cubic inch capacity that is designed to be able to float and keep its contents dry even when briefly submersed up to three feet. Utilizing a fold-seal closure that is secured with a snap-buckle, this bag features an IP66 rating and is suitable for use while on a boat, raft, or whenever there is an elevated risk of the wearer or their backpack falling into water. Aside from providing protection from accidental immersion and the ability for later retrieval, the Classic Waterproof Backpack may also be used for instances where some exposure to water is anticipated, such as while crossing a stream or river.