Personally I loved this story! Vampires on a submarine is a great premise. The author clearly knows alot about being on a nuclear submarine in the 1980s American Navy and that comes through in his work. The Roanoke feels like a living breathing organism, a real and touchable environment. The tension of a sub in this situation and trapped in enemy waters is a great way to put your heroes up a tree then set the tree on fire.
If I have one criticism its just that the ending was clearly where we think the killer is dead but they aren’t, and the last chapter before the epilogue was very unnecessary. Tolkien even made this same mistake in LOTR with Sarumans crime ring in the shire after Sauron is dead. When the action stops and denoument happens don’t try to bring in another action element. It also robbed a tender moment of its deep meaning and patriotism.
That being said that one chapter is my only complaint and the story is incredible. Well written and I hope to see more from this author.