Post History
A further reason is to use the space in the bag for buoyancy and to squeeze the bag into a space securely, by adding air to the bag after it's in place. This generally means a valve on a tube.
Answer
A further reason is to use the space in the bag for buoyancy and to squeeze the bag into a space securely, by adding air to the bag after it's in place. This generally means a valve on a tube.