You dropped through a hole in the ice shelf into an open ocean that has no visible bottom — a drowned world of rock reefs, cave mouths and canyons. Near the surface, light spills down and you can see. But the deeper you sink the darker it gets — until you are blind, and can only listen. Fire a sonar ping and the world flashes back at you for a heartbeat, then fades to black again.
Watch your O₂ — every ping costs breath; refill at air pockets and air-coral. Watch the pressure — descend past your suit's crush depth and your hull buckles. Find plating as you sink to survive the deep. Reach the source at the bottom.