Perform Storage, and Camera Lock with the Wind Waker. Get into a body of water, and hold Up on the analog stick. Link will begin to spin around rapidly, gaining speed with each turn. While strictly holding Up on the analog stick will build up speed, it is possible to gain a much greater amount by altering the angle at which you hold the stick. By holding the analog stick at a precise angle (this angle changes from superswim to superswim, but will always lye within the upper 180 degrees of the stick's range) Link's motion will become strictly back-and-forth rather than circular.
Though the angle varies between superswims, there are a number of ways to determine it. Perhaps the most common method is by using your mini-map and altering the angle of the analog stick until you see the yellow arrow move back-and-forth. This method is somewhat limited, however, because once you leave the quadrant that you started the superswim in the yellow arrow will disappear.
This is where the second method for determining the angle of the analog stick comes into play. This method involves looking at features of the landscape around you to determine whether or not you are moving back-and-forth. Here's how it works: when holding strictly Up on the analog stick you will notice that a feature such as an island will appear on the screen in intervals. However, when you are moving back-and-forth, the island will instead appear to stay in one spot (seemingly behind you), indicating that you have found the proper angle.
Once you're satisfied with your speed, release the analog stick with Link's back pointing where you want to go, and Link will rocket backwards with the speed you attained. You can better judge where you're aiming by opening up your map.
Pressing alternate directions on every other frame while swimming will also cause Link's speed to increase exponentially. This is barely possible on console using lots of pauses, however, and will likely never be worth doing. However it is possible to emulate such an affect by resetting the neutral position of the analog stick using Black Wind. If the correct analog stick angle is acquired, you can then mash down on the analog stick to build up speed (storage will gives you this same effect due to the way the camera works while the glitch is active).
One of the advantages of a storage-less superswim is that you do not need to worry about getting double-storage to prevent your game from soft-locking when you enter a cutscene since the camera is not locked.
The following graph illustrates the correlation of frames and overall velocity for one air gauge worth of time:
The only limit to the speed you can gain is your air meter, and the positioning of the land, including things you can climb up on out of water. You can continuously refresh your air meter if you happen to swim close to the shore of an island without going on land. If you Superswim up on land, your speed is retained, and Link will run backwards. If you go off an edge or back into the water while on land, your speed will reset back to 0. With enough speed, it is possible to reach an island before it loads. Using this allows to be loaded underneath an island, similar to a Wind Waker dive.
Superswimming can be used to cross vast amounts of overworld extremely quickly (much faster than sailing). The sail is still a necessary item, however, as it is impossible to open the triforce charts without it.