Submarines use a prop for forward motion and are almost never 'gliding' using their planes. The purpose of the wings on this craft are similar to the variable-

Submarines use a prop for forward motion and are almost never 'gliding' using their planes. The purpose of the wings on this craft are similar to the variable-buoancy underwater drones that are out there, when the craft is rising the wings are trimmed to cause forward motion and then when it is descending they are trimmed in the other direction to continue forward motion.