This song immediately seemed to me to be about a submarine stalking a ship and then opening fire and destroying it. I'm going from the translation as to the meaning; I get the feeling of the calm, serene, beauty of the submarine following its victim and then, "a firework from the crotch", is the torpedo etc. being fired.
TLDR: Interplay between submarine and target told via the metaphor of a beautiful woman swimming.
This song immediately seemed to me to be about a submarine stalking a ship and then opening fire and destroying it. I'm going from the translation as to the meaning; I get the feeling of the calm, serene, beauty of the submarine following its victim and then, "a firework from the crotch", is the torpedo etc. being fired.
TLDR: Interplay between submarine and target told via the metaphor of a beautiful woman swimming.