Going as far back as WW2, ricocheting a HE round on delay off the ground to achieve an airburst was in the manual. But I don't recall ever seeing it for shooting around corners. (FM 17-12, 1961 for the curious)
80,000 fathoms deep under the sheet and the physics of the hypersaline brine get weird - an ice war nuke on the surface sends a tendril of fresher stuff down and it freezes in the 200 kelvin hell at the absolute bottom of the water column, and it sits there like a shroud
they put the deepest bases where the cryovolcanism and hydrothermal vents get complex. Jovian squids and the trace manganese in the crabs shells plays havoc with the sensors
the old travel holobrochures used to talk up Europa’s serene underground oceans; the majesty of inversed ice cathedrals sparkling below the glaciers… but it’s dark down here. the brightest thing you see nowadays is the firefly glint of the optics on the hunter-killer torpedos