Ok, I'm guessing you're aligning with the Umpani. You need to do your questions in the following order: 2, 1, then 3> Sgt Rubble
Will be found in Upper Mt. Gigas, towards the bottom right of the map, you'll need to use you latest security pass to open the door to where he is.
He'll tell you to suit up with scuba gear (I'll leave it up to you to find them and how to use it, don't want to spoil all the fun for you). Then report back to him to complete that quest.
> Bayjin
Can be reached in two way, either by diving in to the water just near where you just spoke with Sgt Rubble. Alternatively, it can be reached "by land". Go to the Swamp, cross over to the north side of the river, then head top half righthand side of the map, you'll be attacked by Rajin when you're in the right place. Go down the tunnel.
> Sgt Glumph
He's locked up in one of the semi-circle of huts you'll find when you explore Bayjin. Have him join the party and escort back to General Yamir.
I've left alot of the details out, I think this is spoiler enough, but if you need more, let me know.