Well, that's simple!!

While it's not dangerous or anything, as a new model of naval mine, I haven't the foggiest about what sets it off, you know?

It reacts to breast size... no, to childness!! "児気" (jiki) seems a coined word based on "磁気" (jiki; magnetism)

Right now it's just your garden-variety harmless abyssal lifeform!

Unexploded ordnance, yeah? I took out anything that looked like a fuse, though.