How do you make swimming possible with this script?

I'm using the Third Person MMO Controller you can find in the asset store for my game, but i'd like to implement swimming. I would probably be able to do it myself if i wrote the script myself, but as I still don't really understand how this script works.

Its in C#, and im talking about swimming like, you jump through a collider, gravity disappears and you can move around freely(through a bit slower), until you walk/swim out of the water. I'm not asking for a step by step guide, just info on where to put what.

thanks in advance,

Mr.MMORPG