Protecting the Water Way

 is a Fallout 3 quest that is added to the game in the Broken Steel add-on.

Walkthrough
Scribe Bigsley asks the Lone Wanderer to investigate the organized bandit attacks on the Aqua Pura caravans, directing The Lone Wanderer to speak with Officer Lepelletier of Rivet City to learn more details about the attacks. It should be noted that you don't have to talk to Scribe Bigsley at all, Officer Lepelletier will give you the quest as well.

Consult Officer Lepelletier
You can find Officer Lepelletier once you leave the quick travel point to Rivet City. You can find her underneath the water beggar on the first floor of the ramp area entrance of Rivet City. She will explain that a water caravan heading towards Canterbury Commons has just left the Jefferson Memorial and will ask you to travel with the caravan and discover who is behind the hijacking. You are asked to catch up with it, and talk with Officers Davis and Lorin who are traveling with the caravan. Passing an easy Speech check with Lepelletier can net you a plasma rifle and a few micro fusion cells before departing to protect the caravan.

Meet Officers Davis and Lorin north of Project Purity
Following the river leads the player to the caravan just as it is in ambush by three bandits. The ambush point seems to be at a constant location, under the large bridge between the Citadel and the D.C. Ruins. If you hurry there you can save the lives of the two guards but the caravan driver will always be dead. There is also a scavenger camped out under the bridge who will help fight the bandits and can be saved as well. It is rather difficult to save their lives in time without some precognition (i.e. leaving a high-powered follower at the site of the ambush prior to triggering the quest), which pretty much suggests it is part of the plot, to witness their demise.

Find out who is responsible for the attacks
Upon searching any of the bandits you find a holotape titled New Meeting Place from Split Jack, the bandit leader, instructing the bandits to group at Wilhelm's Wharf.

Deal with Split Jack and his gang
When reaching Wilhelm's Wharf, you can speak to Split Jack (the password is "Mirelurk Stew") and pass a difficult Speech challenge to persuade him to give up. Please note that if the Speech check is passed successfully then Grandma Sparkle is likely to be immediately killed by the bandits. Failing that, Jack has to be killed either simply by attacking him and his men, or by joining his gang and then slaying him in a duel for leadership of the gang.

If you elect to join their gang, you will receive a metal armor and helmet, which you must wear before Split Jack will talk to you again. He will ask you to sit down and wait for "other gang members to arrive"; however, no matter whether the player sits and waits or not, no further events are triggered. This is most likely because the other "gang members" you're waiting for are the ones you kill at the ambush. At this time the player can challenge Split Jack to fight to the death, in which case he lets you choose one of three melee weapons to fight with (Lead Pipe, Combat Knife or Nail Board). As long as you fight him with the weapon he gives you none of the gang members attack you, and will instead cheer on the fight.

The melee fight is by no means a push-over, especially on harder difficulties if you stay with the mediocre metal armor you are provided and do not take any drugs. Split Jack has high HP and blocks well, and, more importantly, the item HP of the weapon you get is low, making it quite possible that the weapon will break before Jack is dead. You can replace it with another weapon of the same type, or, even smarter, come prepared to repair the original you are given and do so the instant he gives it to you. If you hit Jack with your fists or any other weapon, the entire gang will become hostile, requiring you to kill them all. Note that choosing Nail Board is especially difficult, as Jack will block almost every swing you initiate and your weapon will deteriorate quickly (Jack's will not deteriorate). Any follower will attack and cause the rest of the gang to become hostile so make sure you are alone or to tell your follower to wait inside Grandma Sparkle's house.

The melee fight can be made fairly easy by switching your armor to Chinese Stealth Armor or popping a Stealth Boy. Keep stealth until your indicator goes to [hidden] then hit him with a sneak attack. Back off and wait for [hidden] again, then repeat. Do this 3 times and you should kill him without ever getting hurt. Another good tactic is to rush in and hit him then back off and repeat, doing this he will rarely get any hits on you and makes the fight much easier. if you have completed the operation anchorage add-on the T-51b power armor is very effective and you will take almost no damage while using knives

After winning the duel one of the unnamed bandits approaches you, stating that while they do not want another leader you should speak with Lepelletier about a "protection" contract; you will be able to interact with them again after making your choice with Lepelletier (see below). It is possible that even if you use the weapon Split Jack gives you exclusively that they will turn hostile after you win the duel, making further dialog with them impossible.

Report to Officer Lepelletier
If you choose not to side with the bandits, Lepelletier thanks you for your assistance, but is unable to reward you and asks you to speak to Scribe Bigsley in order to receive the reward which consists of some captured Enclave gear - Enclave Power Armor and Helmet, a Gatling Laser, a Plasma Pistol and ammo for the same. The quest will finish then.

If you have joined the bandits and killed Split Jack, you will be given two extortionist options that will both decrease your Karma (by 200 points). These dialog options are only available if you've spoken with the other bandits after killing Split Jack. The first option is to blackmail Lepelletier for 500 caps immediately after passing a Speech check in exchange for stopping the attacks. You can tell her that you want 500 caps now, and 500 caps after the attacks have stopped, but she will refuse and still only give you 500 caps. The second option is to make her pay a weekly "protection fee" of 200 caps for the bandits' stopping their attacks. If you choose the latter, you can periodically talk to the bandits at the wharf for a share of the 200 caps for the rest of the game. The quest finishes upon finishing these dialogue options.

If you take any of the evil options, Lepelletier will tell you that she will kill you if you ever talk to her again; and indeed, if you speak to her again she becomes hostile, and so do the Rivet City guards outside ship (but not the City itself). Meanwhile, if you take any option other than the "protection fee" choice, the remaining bandits at the wharf will accuse you of backstabbing them and attack you on sight.

Bugs

 * When you kill Split Jack and receive the note from one of the bandits, the game may freeze after you talk with Officer Lepelletier.