Coherent Convoys

Sequential Movement puzzle

1) Move all ships from the starting (blue) channel through the lock (gray channel) and into the red channel.
2) Add the small spacer at the blue end of the lock, then move all ships from the red channel to the blue channel., except that the guard ships (light red and light blue) will remain in the lock.
3) Add the large spacer at the red end of the lock (remove the small spacer), then move all ships from the blue channel to the red channel, again leaving the guard ships in the lock.