In order to swim across water and reach the Frozen Grotto which is a cavern where you will find a temple inside you will need to obtain Zora's Flippers. This Where to find Zora's Flippers Guide will show you how to get them.
Getting Zora's Flippers is not easy as they are hidden away in an area of the game that can be easily missed. This area is near the Frozen Grotto, which is two screens directly south of Hyrule Castle, connected to Lake Hylia. This is a large area but if you look in the top left corner of Lake Hylia you will see the entrance to the cave of the Zora Prince where there will be 5 floating ghosts inside, the one on the right you can speak to. These floating ghosts will not move as they are guarding the sleeping Zora at the top of the room.
To obtain Zora's Flippers you need to make sure you have some bombs equipped. Cadence of Hyrule gives you bombs relatively early on and you will need 5 of them (you can break the pots at the top if you are short) to blow up each of the ghosts. When you manage to kill all 5 ghosts Zora will suddenly wake up and if you talk to him he will give you his Flippers which will then allow you to swim across Lake Hylia and reach the Frozen Grotto or any other deep bodies of water you find in the game.
Check out our How to Get Better Weapons Guide to find out how you can get weapons that will make the game easier.
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