The Covenant of Water question

I just finished it this week. The way I understood it was that "the condition" essentially triggered a sort of vertigo whenever water would get inside the ear canal (I may be misremembering here so forgive me or correct me if I'm wrong). So even in shallow water once submerged one has no way to tell where they are or what way is up.

The fear came from those who had the condition knowing that water triggered "something" in them and was extremely dangerous and so they stayed away and avoided it as much as possible.

That's the way I understood it.

I just finished this book, one of the best I have ever read. As I read it, men with the 'condition' became completely disoriented in the water, almost helpless which lead to their drowning.

NFT discussion aside, did anyone have any thoughts as to why it is Elsie that escapes her families medical condition. In the end it almost seems like she blames herself for passing on the condition of "leprosy" as she calls it.