The Seahorse’s Request
The moment you enter Pinnacle Rock, dive to the sea floor, and release the Seahorse that you’re carrying in a bottle. The Seahorse has a request for you and asks that you follow him.
Remain on the sea floor and walk around, following the Seahorse through the murky water. Follow the Seahorse’s exact path, or else you risk getting lost in the murk. Navigating these waters would be tough without the Seahorse’s help.
When you reach the depths of Pinnacle Rock, the Seahorse borrows your map and marks the route that you took to get there for future reference. He also tells you that his friend is in trouble nearby. The Seahorse asks you to rid the area of all of the dangerous sea snakes so that his friend can be rescued. Snakes… Why’d it have to be snakes?!
Slaying the Sea Snakes
A deep pit lies just ahead, and its walls are lined with several tunnels. A giant sea snake lives in each tunnel, and it darts out whenever you swim near. You must slay all of these giant sea snakes in order to save the Seahorse’s friend, so swim directly at them, and hold 
+ 
to bring up Zora Link’s magic barrier. Swim around and hit the gills on the sides of each sea snake’s head twice to defeat it.
If you ever run out of magic power and Magic Jars, you can still slay the sea snakes. Just swim up to their tunnels from the side, and carefully land on the tunnels’ outside edges. Once you’re standing on the outside edge of a tunnel’s mouth, aim and throw Zora Link’s fins (hold 
and release) at the sea snake’s gills after the monster emerges. You can’t actually lock on to the sea snakes, but they’re so big that their vulnerable gills are easy targets. Try this out on the ones at the bottom first; they’re the easiest to approach.
Two of the sea snake tunnels contain treasure chests, while three other tunnels contain Zora Eggs—the last three eggs that you need. Keep an eye out for these treats, and scoop all three eggs into Empty Bottles as you go.
Slay all of the sea snakes to save the Seahorse’s friend. The two are overjoyed to be reunited and give Link a Piece of Heart as thanks for his help. Way to go, hero!
Piece of Heart #39
You got a Piece of Heart! Collect four Pieces of Heart to assemble a new Heart Container. Each new container you put together increases the amount of life energy you can have.