He didn't have to call for help, simply fall to the side and drag himself back in to the cool sea for some more shrinkage.
But in reality, there might be some orientation changes - hanging down low vs. sucked up tight during temperature changes, but actual nard size doesn't vary with temp. That business is for other parts.
Or stay calm, order a drink (on the rocks), and discreetly reverse the process...though you're right, there's an anatomical/physiological problem with the shrinkage explanation.