Swimming

Swimming is a somewhat important but mostly optional mechanic. If you decide to go underwater, or want a good technique of farming Teraphyxes, then you may want to invest in improving the skill associated with swimming.
The swimming skill determines how long you can swim for without getting tired. It starts out as level 20 by default every time you start the game.
To raise the swimming skill, you just simply swim around, but remember to get back on land before the swimming stamina bar goes down entirely. If you fail to do so, you'll get stuck underwater and you will eventually drown.