I should post this before someone steals it.
Fast forward:
At the end of this chapter you must start some cannons or something, instead run along the coast line, past the Wraith until you REACH a piece of drift wood between the cliff and the water.
Now the trick part. walk on the drift wood, looking straight ahead you will see a ledge and if you jump and jetpack you should be able to make it. once here you have a huge area you can freely explore.
Points of interest:
Loner marine - so far I haven't noticed anything different from this guy, other than him being alone. He might just be a lucky AI from the previous attack.
Skating Ring - When you jump in the water you just float like you are jet packing...its pretty fun.
Crash ship - During a cut scene you see a civilian ship get shot down - you cant really do anything with it but you can get a better look at it.