Right, it is nonsensical to put a manikin in an available empty seat right next to the exit but makes perfect sense to squeeze it onto the lap of one of the passengers. Who then passes it forward like a football, as he goes to the back of the plane (right by the empty seat) and then magically has the manikin appear next to him with bone dry hair in the water.
So why in this image that you provided is the manikin hair bone dry?

It's entirely your
conjecture that the mannequin's hair is bone dry in that picture.

Certainly the way we see plunge JK headlong over the railing and into the water suggests he had little regard for keeping anything dry, even an old iPhone in his left shorts pocket. It looks as if at least the right half of his body got all wet:

A mannequin's wig may not soak up water the way you might expect, or when JK may have thrown in onto the water (afterward for you to find his right hand empty), he would have some justification for rushing headlong out of camera's view--for the most part--to retrieve that mannequin. That mannequin body may not have sunk into the water much at at. Even the original Ms Fuddy's body stayed atop the water amazingly well.
In every picture we absolutely know must be of Jake and can't be a mannequin, JK's hair is brown, not red even in direct sunlight.
Furthermore, you've never answered how Jake's hair only only comes to the top of this shoulders and this red hair in the picture comes down at least to his mid back, perhaps lower.
WE’re supposed to believe that his hair was that curly and went down his back that far and yet when he was in the seat there was no hair sticking out under his clue cap - not even the straight black hair that we SEE sticking out under his cap when we’re sure it’s him?
I hope my previous post didn’t get stuck in moderation: Where is his right arm in that image?