I've read this three times now, so I've just about managed to get past the stage of 'oh Christey, the hotness' and started thinking about the storyline and how intrigued I am by what's going to happen next! This series is also the only fic I've read where I haven't had the het squicks (and you seems to have converted many others) and as you said it's because Tia's not emotionally involved - and because she rocks :) I also quite like seeing this as an extended metaphor (dunno if I'm reading WAY too deeply into the pr0n). Tia is the sea, and the sea is what brought Jack and Will together - literally and figuratively!
Oh, and I love Possessive! Jack too, hee! I picture him clutching at Will with the same damn expression on his face as when he's pouting over his jar o' dirt. Great, great writing from you as always. Funny, and hot. That's my OTP :)