There is a bug with the shallow water that allows you to be running or even sprinting in it if you follow the correct steps.
First off you have to be in either the running or sprint speed. Then you jump off a cliff like a maniac into some shallow water
that is directly adjacent to the cliff. So long as there is only a sliver of land separating you from the water, when you enter it
you will maintain your previous movement speed until you do something to cause it to reset and make it realize you are indeed in water.