If you are on the run for the skyshards of Hew’s Bane, this would be your second or third in line. As soon as you leave the main city, head northwest. Enter the solo dungeon and head toward its largest room, in the southeastern part. This is where you fight the dungeon boss The First and Magnifico Bahraha.
In the same room where the bosses are, you can spot a large broken wooden ship. Go behind this ship. There is a small entrance just behind it. Go through it and follow the path. This path is essential for reaching the shard. It takes you over the platforms and their wooden boards toward your final goal. So, be sure not to fall down. This path will eventually take you toward the entrance of the dungeon and the shard. Therefore, it is advisable to complete the dungeon’s quest “A Secret Shame” before you decide to go here. Just to save some time…
Bahraha’s Gloom entrance.
Find and go through the hidden entrance.
Follow the wooden board path, from room to room.
It eventually leads to the dungeon skyshard.
Sand Kingdom Moons - Super Mario Odyssey Power Moons