[Perceived] Beneath the thick ice, a long, sinuous form slips by like a late-afternoon shadow—but out on this flat expanse it’s no trick of the light. With a twist it sinks, vanishing into the inky depths. [Attacking] The ice heaves, then shatters! Fissures splinter out in every direction as bony, cart-sized heads punch through the surface, sending shards flying. The mouths take sweeping bites.