Sometimes opening a treasure chest is as simple as approaching it in The Legend of Zelda: Tears of the Kingdom. However, in the case of The Treasure Hunters side quest, you'll need to get the treasure chest out of an unreachable spot.
Prissen and Domidak are both attempting to get the treasure for themselves, but since they lack the abilities that Link has, it's a great opportunity to make the treasure your own. Here's how you can claim the treasure chest.
Where To Find The Treasure Hunters
You'll find this side quest as you begin to travel further north from Hyrule Castle. The Treasure Hunters will be in the Great Hyrule Forest region, directly north of Hyrule Field. Start by crossing Helmhead Bridge next to Hyrule Castle, and you'll find Prissen and Domidak down the path going east towards Rauru Settlement Ruins.
When you approach the two travelers, they'll mention that they are attempting to get the treasure chest in front of them. However, it is stuck on a platform within a pond of sludge, making it impossible for them to reach it on foot. Luckily, Link has some abilities to make it an easy grab for him.
How To Complete The Treasure Hunters
The only way you'll be able to successfully pick up the treasure chest is by placing a platform that will allow you to jump across the lake. Follow down the eastern path towards Rauru Settlement Ruins, where you'll find a Hyrule Restoration Materials location that has multiple wooden boards for grabs.
Pick up one of these boards using Ultrahand, and start bringing it back over to the pond where the chest is. Unfortunately, if you place the board directly in the pond, it will immediately float to the bottom. Instead, you'll need to prop it up on the five metal stakes sticking out of the mud.
Place the wooden board on top of these stakes as shown in the image above. Then, jump on top of the board and walk to the end. Use Ultrahand to pick up the treasure chest, and rotate it to bring it back over towards the two men.
Now, get back up on top of the cliff and place the treasure chest in front of you. When you open it up, you'll receive 3 Bomb Flowers. Return to Domidak and tell him about the treasure you found, and Prissen will then mention Misko's treasure which they are also after. They will both provide you with leads to finding Misko's treasure, allowing you to start the hunt for some more substantial treasure.