Hold the fuck on, that dude is there BECAUSE its his job to protect them from mermaids? Why the fuck did he let 2 people die last chapter then?
Is this dude secretly a psychopath???
He is doing a three man job all on his own because the captain cheaped out, and was already vomiting blood on the second night: if they want to survive as a ship, he has to start at the very last moment and end as soon as possible. This means the ones more sensitive to the song are not completely covered, but I don't think you can fault him for that...