@bigbossmalone I found this kinda difficult too, if you move each man it is easier as they do not spread out and go in to the water, you just need to move directly ahead towards the nearest little islands, going basically all the way around the swamp before coming to a couple of bridges on the right. I advise using someone with a silenced weapon, that way if you target the guards along the way and take them out, the snipers will not be alerted and you can move up no problem.
What I did was sent Merill up to clear the way and he rescued the prisoners on his own, then i moved the rest of the guys up one by one at like 15 feet a time so they were still together but they were not drowning, moving the whole group is a nightmare as they spread out in to the water.
Fortunately this is the only swampy section so as soon as you are through you don't have to worry
