I think I've accidentally found a glitch. Okay as soon as you start go jump down to the right side and hug the left corner. If you did this before Drake started chasing you down there he'll stick by the ledge (so basically right on top of you to the left) and will just stand still.
He'll continue activating his level 3 really fast but he won't do anything afterwords. He might shoot once here and there but from that angle it can't even get you.
I just did this trial twice this way so I know it wasn't a one time thing.
found this at gamefaqs and it works perfectly, so if your like me and raged for 48 hours over this one trial try this out
Solved! Go to Solution.