to dive mor than six meters you must go to the fishing hole as an adult and catch a twenty pound fish the guy will give you a scale that allows you to dive deaper to catc hthe fish i suggest you go out on the middle log in the middle then cast from there right by that log is a really big fish try to catch him
You need the gold scale which you can win from the fishing hole as adult Link or you can equip the Iron Boots to make you sink in water and the Zora's tunic to allow you to breathe underwater.
You can dive underwater after you obtain the water dragon's scale, which you'll receive in Farore's Silent Realm later on in the game.
You can only dive off of docks, off of your Loftwing, or in certain places with deep holes, such as in the Eldin region
You have to obtain the scale after the third dungeon.
**SPOILER**City in the sky is also a dungeon level. Go to the shop in the city, (its located a little ways passed where the pool of water is) talk to the Oocoo. This will make the game continue on. A scene where a huge bird flies into the city should occur. Your goal is to kill it.
You never kill Zelda.
You must have acquired the Water Dragon's Scale. This is recieved by following the main questline
You have to get the Water Dragon Scale by completing Farores Trial in Faron woods
First you will need to get the Water Dragon's Scale from the Faron Woods Silent Realm. Once you obtain it you will be able to swim underwater, there is a secret opening at the bottom of the tree underwater which will let you inside the tree.
Breathe under water
To get the water tunic you have to find or buy it.
You have to beat the forest temple and go back to the sword pedestal in the temple of time. Talk to sheik and he'll let you put the sword back. If that doesn't work, try after beating the water temple.
Water dragon scale while looking for the flame in Faron forest
you need to get 10 power gems then you go to sprit island and talk to the water thing and click on power.Then you goto colletions and tap the spirt of power and there you go!
In Skyloft go acrossed the bridge above the water to reach the other side. On this other side go up past the first two houses and look for a hole leading to a path down to a house, this is the fortune tellers house.
You should try a walkthrough