Gaia Falls Islet

Sail east of Yamata to find a beach and a cave.

Go down the stairs here. Pretty scene. Unfortunately, when we get down to the bottom, that waterfall will make it impossible to continue to the left, so aim for the southern exit. You'll be on the world map, but just go into the next cave to come back.

In here, you can move up and grab yourself over to the left and find the Umbra Cloak. Now go back across the gap. We can make our way up the water on this side by using the poles and grabbing from one to the next. Go up and use the big rock to edge yourself to the spire. Just take your time here and don't fall to the lower rock. On the second grab, run to the left to reach dry ground. Go up and grow the vine to reach the chest, but it's a Mimic! Defeat it go gain an Apple. Now go down steps and behind the waterfall you'll find the Mercury Djinni Shell.