This challenge is part of Brutus' Briefing challenges, the first agent Fortnite Chapter 2 Season 2 focuses on. You'll have to search a total of seven chests in two of the season's newest locations: The Shark or The Grotto.
The map
These locations are all the easier to find as they're specifically marked on your map. In addition, they're advanced bases of the Henchmen. You can find many chests there, including accessing hidden rooms by scanning your face on locked doors.
Here's everything you need to know about the new Fortnite Chapter 2 Season 2 Brutus' Briefing challenges and rewards.
