The entrance to Shark’s Teeth Grotto is found in the southwestern part of the Hew’s Bane island. This is one of the rare dungeons that takes place outside. This may be confusing, since the shard is marked as being “underground” on the map.
Once inside the dungeon, we’ll need to head to the upper level. In the northern part of the dungeon, you’ll find a path toward the higher areas. The two arrows show one of the climbing routes. Once you are up, head to the large platform just above the dungeon entrance area. The shard is located on top of the wooden platform, close to one of the enemy groups.
Sand Kingdom Moons - Super Mario Odyssey Power Moons