I'll bite. What is the significance of the submarine? Or is it strictly Freudian?
There is nothing in the entire doujin that references a submarine... so I think it's just because he thought it would be cool and whimsical or it's an sideways Kancolle ref (school swimsuit = subs).
Poyoyon❤RockOur summer begins in Ariake, and ends in Ariake.
Ariake is where Comicet is held at Tokyo Big Sight, where this doujin was sold. You could also read this as 'dawn'.Simple Fetish Series 15THE Under Middle School Student 2