Few realize that Headstone Island is an alternate entrance into the Earth Temple. Long ago, a giant stone head sealed off the entrance (and gave the island its name). Lift the massive stone head with the Power Bracelets, toss it aside, and enter the Earth Temple dungeon.
Treasure Chart #14 (via Submarine)
Treasure Chart #14 is found inside a submarine. Sail to the submarine, climb onto it, and enter the doorway leading inside, but be prepared!
As soon as you enter, you’re thrown off the balcony and into the main area, where several Bombchu and Bomb Plants wait to drive you insane. Eliminate the Bombchu quickly by 
-targeting each one and using the Boomerang. This way you can fire and forget. Using your sword can be dangerous, as Bomb Plants detonate shortly after being struck.
You can’t escape this submarine until you wipe out every Bombchu. An escape ladder leads to the balcony, but it’s blocked by fire until you defeat all Bombchus. Then the fire disappears and a second ladder drops from the ceiling, leading up to a chest that contains Treasure Chart #14.
Piece of Heart #20
If you have a Hyoi Pear handy, you’re in luck. A Piece of Heart sits atop the highest spire. Take control of a seagull and fly directly into the Piece of Heart.
Silver Rupee (via Treasure Chart #40)
Find and open Treasure Chart #40 (found atop a Sea Platform in Southern Fairy Island [D6]) to pull a chest from the Great Sea near Headstone Island. The chest contains a Silver Rupee.
Earth God’s Lyric
If you have the Power Bracelets—found inside the Secret Cave at Fire Mountain (F3)—lift the giant stone head and throw it away, revealing a cave. Enter, and you come to a large stone tablet. Use the Wind Waker near the tablet to learn the “Earth God’s Lyric”; you will use this to find the Earth Sage and at points inside the Earth Temple dungeon. To play it, hold 
for 6/4 tempo, then play 
, 
, 
, 
, 
, 
.
Mirror Shield
Hidden in the Earth Temple dungeon is the Mirror Shield, which is capable of reflecting beams of light. Refer to the walkthrough for more information on the Mirror Shield.