An inflatable device is provided, and contains a body and a mouth. The mouth is positionable in an open position and a sealed position. The body includes a flexible body wall that defines an interior volume. The body defines at least one air flow path from the mouth through the interior volume. The air flow path has an air flow path axis and has a cross-sectional area. The body further includes at least one structural member that applies a force on the flexible body wall transversely outward from the axis so as to urge the flexible body wall towards a transversely expanded state. The body is movable between an axially collapsed state and an axially open state along at least a portion of the air flow path and is urged towards the axially expanded state by a force applied by at least one of: the at least one structural member, and air flow into the body through the mouth when the mouth is held in the open position.