Lakeside Laboratory

The 'Lakeside Laboratory is a lab where an old man works. He researches the life in Lake Hylia in The Legend of Zelda: Ocarina of Time. He is similar to the man at the Marine Research Laboratory at the Great Bay Coast in The Legend of Zelda: Majora's Mask. Here you can dive in the pool, and the old man will tell you how deep you went. If you touch the bottom he will give you a Piece of Heart.

Also, there is a patch of soft soil outside the Laboratory where you can plant a Magic Bean, enabling access to the roof. The roof can also be accessed by using the Scarecrow's Song.

Trivia

 * If you use the Zora Tunic and the Iron Boots to sink to the bottom of the pool, you will see a cage with a motionless shark.
 * At the bottom of the pool of water are many red rupees.