Complex sentence: Helena inventories their supplies and finds that a corrosive chemical, normally stored in the engine compartment, has smashed through into the cargo section; the acid has contaminated most of their consumables, leaving only survival rations and two containers of potable water.
Split into simpler sentences: Helena inventories their supplies and finds that a corrosive chemical, normally stored in the engine compartment, has smashed through into the cargo section. The acid has contaminated most of their consumables, leaving only survival rations and two containers of potable water.