The Golden Scale is a significant item found in The Legend of Zelda: Ocarina of Time that gives Link the ability to dive deeper. You get the scale by catching a large fish from the Fishing Pond when you go there as Adult Link. This guide will show you how to reach the Fishing Pond and catch the fish needed to earn this item.
How to Get the Golden Scale

In order to obtain the Golden Scale, navigate to Lake Hylia as Adult Link and find the Fishing Pond. The location can be obtained with the Scarecrow’s Song. Also, you can use the Magic Beans if you have already planted them by the Laboratory before.

When you enter the Fishing Pond, you should meet the worker at the reception and start fishing right away. Your aim is to catch a fish that is no less than 60 cm long. To do so, you will need to find a big fish and throw the line close to the fish. Move your line a little to direct its attention toward the bait.

As soon as a fish bites, push ZR and turn the stick according to the fish’s direction. If the fish goes left, move left and if the fish goes right, turn right. You should be quick when moving the rod because if you resist the fish, you will create too much tension for the line.
Continue tracking the fish until it becomes exhausted. When it starts moving slowly, begin the process of bringing it in. It effectively becomes easier to fish when it is raining. Once you catch a fish measuring at least 60 cm, return to the counter to inform the attendant that you have completed the task. You can then claim your prize and receive the Golden Scale.
How to Use the Golden Scale

The Golden Scale permits Link to plunge deeper into the ocean. Its primary purpose is to get a Piece of Heart in the Laboratory located at Lake Hylia.

Make your way towards the Laboratory that is opposite the Fishing Pond, and jump in and dive down into the pool. Once you have used the Golden Scale to dive down, you will also be able to pick two Rupees submerged underwater.
When you leave the pool, you will be greeted automatically by the attendant of the laboratory, who will reward you with a Piece of Heart.

