
In Dead Island 2, there is a subcategory of side quests called Lost & Found quests. These will generally ask you to follow a trail of clues to find a hidden item. The first one you’ll probably encounter in the game is called “The Clean and Snatch,” which asks you to find an antique sword hidden by a pool boy named Obi.
This quest becomes available once you complete the main story quest “O Michael, Where Art Thou?” and begin “Kwon with the Wind.” It will appear as a red exclamation mark icon on your Beverly Hills map.

After talking with Rikky and Roxanne to start “Kwon with the Wind,” you can find the first piece of the Clean and Snatch puzzle in their pool. But first, you’ll need to disable the power that’s electrocuting the water.
Here’s a video of exactly how to do this:
In the pool, you’ll find a note that says:

Apparently, Obi the pool boy stole a sword, and he’s planning on leaving Los Angeles for good. But before he goes, he’s making one last round of the pools in Beverly Hills to make sure he collects all his tips. This clues you in on where to find the other journals: in pools around Beverly Hills.
The next clue is Dave’s Phone, which can be found in a nearby pool. It’s at the house directly north of where you picked up the quest, sitting beside the pool. Here’s where it is on the map:

And here’s a video of the exact location:
And here’s the text from this phone conversation:

The important clue here is that the pool you’re looking for is in Bel-Air rather than in Beverly Hills.
But before you go marching back to Beverly Hills, you should find the last clue in Bel-Air. That one can be found in the pool at Michael’s house. In case you don’t remember where that is, it’s right here:

Here’s a video that shows the exact location of the note you’re looking for:
And here’s what the note says:

Apparently, Obi “borrowed” a unicorn rubber ring from Michael so he could lend it to his girlfriend. See, she has one for her pool, so Obi thought the two of them could be friends. He also mentions that his girlfriend has a pizza floatie. So this clues you in that the pool you’re looking for should have both a unicorn and a pizza floatie in it. Do you remember seeing anything like this?
The pool you’re looking for is the one at the Goat Pen in Bel-Air.

When you get there, you should find the zombified version of Obi. He should be labelled “Obi the Pool Guy.”

If you kill Obi, he’ll drop Obi’s Key, which you can then take back to Beverly Hills to open the chest to recover the sword. Remember where you picked up the note to start the quest? That note was on top of the chest that you’ll now be opening.

Inside the chest, you’ll find the sword that Obi was talking about. It’s a Rare Electrocutor Officer’s Sword, and it should scale up to your current level. I was Level 9 when I got it in my guide playthrough, and here are the stats at Level 9:

Remember, you can repair the weapon if it breaks, and you can level up the weapon to your current level whenever you level up (so when you hit level 10, you can upgrade it to a Level 10 sword, for example). You do both of these things at a workbench, and both of them cost cash.
And if you want the last bit of Obi’s story, the chest also contains Obi’s phone. You can read the message that sent poor Obi to his demise:

And that’s how you complete the Clean and Snatch Lost & Found quest in Dead Island 2!