A Dead Man's Protocol

Humanity was nearly wiped out by a mysterious virus before fleeing to the sea, only 20% of the population remaining. Nearly 4 centuries later, mankind has just begun to reclaim lost land, the number of zombies dwindling and the effort aided by a new kind of soldier. They're stronger, faster, more adept at combat in nearly every way, perfect for the slaughter to come.
So what happens when a research assistant near the bottom of the food chain exits the sea base, accompanied only by a team of bloodthirsty maniacs? In a desperate attempt to finally make a vaccine for the deadly virus, First Officer Vax is sent off to gather tissue samples of mutant zombies, only to have his every step toward making it out of this mission alive thwarted.
Is this sample even enough, or is man forever exiled to the ocean? What happens when these mutants gain intelligence beyond what anyone could ever be prepared for? Countless questions surround every mission, and no one seems inclined to answer any of them.
The only thing Vax knows for certain is that the White Demon of the Terra Force, Lieutenant Adek, is out for blood.