Some resources are easier to get than others in Grounded, and Pond Moss is one of the more difficult ones. Not only are there some prerequisites to getting this item, you'll also need to know exactly where to find it on the map. Thankfully, there's Pond Moss in abundance at certain spots on the map if you just know where to look.
Pond Moss Locations In Grounded
Pond Moss is a little rarer than some other objects in Grounded, only being found in some very particular parts of the map. Generally, if an area is swamp-like, it's likely it'll hold some Pond Moss. But there aren't a lot of swampy or marshy areas on the map.
Despite its rarity, there are a few hot spots that you'll definitely want to check for Pond Moss. You can find Pond Moss in the moat, in puddles, and in the Undershed Sinkhole. To get the Pond Moss at these locations, you'll need to check out the bottom of the body of water and grab the green moss.
Remember that to harvest Pond Moss, you'll need a Widow Dagger. This is a Tier 3 weapon, and to make it, you'll need to have killed a Black Widow since you'll need Black Widow parts. This means you might not be able to get Pond Moss early on in your journey.
If you don't have a Widow Dagger quite yet, you can also get Pond Moss from killing Spiny Water Fleas. This isn't a very common drop, though, so you're probably better off searching in the areas where it's known to spawn once you do get a Widow Dagger. This drop is so rare that you could kill over twenty Spiny Water Fleas and still not receive a single piece of Pond Moss.