Hidden bonuses: 5
Level walkthrough: Keep moving forward and don't forget to continue using your biotic arm. Notice that your character has serious problems getting out of the water, so your main concern from now on will be to walk only on stable surfaces. You'll soon hear a warning about enemy snipers. Head forward and then turn left. The first bonus item can be found near the water.
There are two passageways leading to the area occupied by the snipers. You may choose the main path or you can proceed to your right to find an alternative route. Either way, you should now focus on eliminating all snipers. Start off by getting on top of the nearest building.
Each time you plan on eliminating a new sniper you should approach him quickly and perform a melee hit. Doing this not only will allow you to save ammo, but you'll also complete side challenges. Try securing this entire area and jump between buildings using your bionic arm to avoid drowning.
Once you've taken care of all the snipers return to the building where you saw the first sniper. He's probably still alive, so you'll have to use one of the holes in the wall to reach him. Neutralize him quickly and notice the second bonus item in one of the rooms. You'll have to go through a smaller hole to get to this object.
Don't leave this area just yet. Instead locate a beam hanging out of the wall of the building you're standing in. Attach yourself to this object and start swinging in order to reach the third bonus item. Remember to prevent the main character from landing in the water!
The fourth bonus item can be found near one of the smaller buildings located on the right side of the main street. I would recommend that you acquire it by landing on the small platform from the roof. Continue moving towards your current destination.
Watch out, because you may end up being attacked by a few additional snipers. Make a leap towards the building located closest to the checkpoint. Ignore the bridge for the time being and inspect the area under it. You shouldn't have any problems finding and collecting the final fifth bonus item. Get on top of the bridge and notice that you're being attacked by a new sniper.
Start heading towards the last sniper and make a few jumps along the way, so you'll remain on the destroyed bridge. Once you've arrived at the final area deal with the sniper by throwing a few swift blows and enter the tunnel to end this mission.