In Ocarina of Time, the shop can be found in the lowest level of the Domain, and can be entered when Link is an adult. This shop is the only place that you can get a Zora Tunic, which you need if you need later in the game. If you are a child, you can melt the Red Ice with Blue Fire and get in the shop, but King Zora XVI gives it to you for free if you melt him.
The shopkeeper is know for selling easy-to-catch fish at an outrageous price. He also sells a variety of other things, at not such ridiculous prices.
Items Link can buy
5 Deku Nuts
You can find the Zora Shopkeeper in the Zora Shop inside the Zora Hall. There is nothing here that you can't find at other stores, and it is more expensive than said stores.