You can find this collectible on the western coast of a nearby river. Its location is just northwest of the large lake island nearby – where Four Quarry Islet POI is (eye icon). If you are following the coast from north you are going to walk by Black Vine Ruins dungeon and Silvenar Vale Dolmen.
Shard, itself, is on top of a small boulder and is guarded by three hostile leopards.
Sand Kingdom Moons - Super Mario Odyssey Power Moons