Ah. The "springs" or Enchanted Springs are a place in Atquati.
There you will have a random event occur each day you swim there. {depending on what tier you are}
From there, if you go once each day, consecutively, {if not you'll be reset to level 0} random events will occur.
Anything from gaining/losing tu, getting an item or getting a colour change as mythies said.
Ah, and don't forget this is where quelis came from. You can randomly find an egg when you swim there.
That is, if you are tier three {or if you have gone there for 16 or more days straight}
This is also the rule for colour changes.
You can find more items as your tier goes up.
There are three tiers, one, two and three.
Prize Tier 1: 0-5 consecutive days
Prize Tier 2: 6-15 consecutive days
Prize Tier 3: 16+ consecutive days.
Hope this helps! (: