To prevent dead zombies from resurrecting as faster "Crimson Heads," you must burn the corpse using a Lighter and Kerosene or score a clean headshot (decapitation).
After un-flooding the room, you must use specific valves (often randomized, check the whiteboard) and lower the shutters to trap the Neptune sharks. Resident Evil HD SWITCH NSP
If playing as Chris and you failed to save Richard, you will switch to Rebecca Chambers to craft the V-JOLT. To prevent dead zombies from resurrecting as faster