So, with the reveal of aether balance in sentient creatures tilting to one aspect too harshly resulting in distinct physical changes (toward darkness leading to Voidsent, toward light leading to Sin Eaters, etc.) I came to wonder about the changes to our pirates chaps from Sastasha and how they came to become more sealife-like (obviously modelled after a particular crew from a certain popular pirate film). I don't recall (nor found) evidence of Leviathan being involved in it at all which could push their aether to tilt toward water and looking back at what text I could find online about the dungeon and the characters I haven't found anything conclusive.

Does anyone know what exactly befell our Serpent Reavers that caused them to change as they did by the time we adventure into Sastasha (Hard)?