No Way Out? (Patreon)

Nav' Girl cadets Misako and Nami are engaged in Advanced Breathheld Maneuvering (ABM) exercise, whereby the duo was called upon to swim through an extensive covered waterway  ("the Runway") to emerge up through small portholes and into the Tank, all under the pressure of 20 meters deep. 

One miscalculation: although the porthole was a non-issue for Nami's slim torso, Misako's body got stuck around her breastline and would not budge. She tried a couple of different holes but noted she had the same problem.

What are her options? Apparently no time to go on a diet now...she needs to think hard while her lungs can still feed on their stale contained air. But the 5 + min heavy breathheld exercise is starting to take its toll...