So we all know this quest is very, very bugged. One specially annoying is that it's impossible to do the sneaky route. No matter how high your skill or what your buffs are.
I've recorded this from my phone (maybe someone knows a way around it without needing to storm in) and uploaded it here: http://www.youtube.com/watch?v=1Kxt7hop2Kg

So yeah.. as you see, I'm max Sneaking, no armour that could make me detectable, even wearing muffled boots and have the Shadow of Nocturnal which is if I'm right the strongest invisible spell.
But still, as soon as I get near the water or just get in, I'm detected somehow.

Soooo... anyone got a fix? Idea? Way around without needing to rush through?