Why submerged submarine kills are so rare

Why did the United States record no submarine-on-submarine kills in the Pacific War?

Because submerged submarine-on-submarine engagements were exceptionally rare; surface attacks on submarines are counted differently.

The comparison concerns attacks in which both submarines are submerged. American submarines did sink submarines caught on the surface, but those attacks do not answer the narrower question. The exceptional British wartime example required calculating a shot against an underwater target without the fire-control equipment that later submarines would carry. Accidental collisions are also excluded from this count. The absence of an American success in this category therefore needs to be understood against the rarity of the engagement itself.