“The Fishing Job” is a Thieves' Guild Faction Quest in The Elder Scrolls V: Skyrim
These quests have to go to a city and pickpocket a particular item.
There are no negative consequences with the Thieves' Guild if you fail a quest. Just a reminder from either Vex or Delvin not to get caught.
To complete this quest, take your time. Move to the marked area. Watch the movement pattern of your target. Once you understand it, move in and quickly pick their pocket. Remember to move in crouched. It helps to augment yourself using Magic and Potions.