In this guide, you will find out how to unlock the chests on Dragon Beach in God Of War Ragnarok. You will find the first rune behind the waterfall, so head there and smash it with your axe back. After that, take your axe back.
The next one is located behind the wooden fence, you have to shoot your axe at it to smash it.
The last one you is located in the water stream, you have to freeze the water and smash it using your axe. After that, you can have a look at your chest.