“I can’t tell you if the merfolk were mocking you or not, Elsa. I will only say that we must be careful not to anthropomorphize other animal behavior, despite how similar they appear to us. Having said that, it is a fascinating idea, and I would love nothing more than to spend an evening debating the matter with you. To do that, though, we need to find a way out of this bloody tomb. Any ideas that don’t involve us getting eaten alive?”

“I was hoping you might have one.”

He was silent for a long moment before saying, “The bag I dropped. We need to retrieve it.”

She blinked. “I forgot about that bag. I meant to ask you what was in it when we surfaced in the first air pocket…?”

“An assault rifle,” he said matter-of-factly.

“An assault rifle?”

“An amphibious one, yes, designed specifically to be fired both on land and in water.”

Elsa laughed, a braying cackle. “You’ve got to be kidding me! No—please tell me you’re not kidding me.”

He wasn’t. The United States and the Soviet Union became interested in underwater firearms when the two countries began deploying underwater saboteurs during World War II. The problem they faced was that water was bulletproof. Traditional bullets lost their trajectory and penetration ability almost immediately because drag at high speeds was much greater in water than in air. During the early Seventies, the US Navy introduced the first underwater assault rifle that fired dart-like bullets. Around the same time, the Soviets created a more sophisticated assault rifle that used the phenomenon of supercavitation, in which a blunt-nosed projectile created a bubble around itself to reduce drag. The weapon was used by Soviet and Russian Navy special forces for more than forty years until it was recently replaced by the ADS amphibious rifle—which was what was in the black ripstop bag on the floor of the lava tube.

“I’m not kidding you, Elsa,” Marty told her. “The weapon went into mass production last year in Russia. When it became available for export several months ago, I was able to get my hands on one.”

She wore a bemused expression. “So you could hunt merfolk?”

“I’ve always believed—or hoped—it would only be a matter of time before Pip and I located merfolk. When we did, I wasn’t going to take a picture of one. Even a high-definition video wouldn’t convince skeptics, not after the Netflix debacle. I would need a specimen, dead or alive. Preferably alive, but how the hell was I supposed to accomplish that? Which meant I would have to kill one, and I didn’t think a speargun would do the trick.”

“You were planning on murdering a merfolk on this dive?”