Some ideas for a possible new area/level for Sky: Children of the light (ThatGameCompany).
Waterfalls, although beautiful, would be dangerous, draining your light if you dare to cross them. Secret areas or bonuses could be hidden behind them though.
In case your Skykid were to be dragged by the water, he would end in the rapids area below, where giant crawlers would patrol the ceiling, reacting to movement. Flight would thus not be recommended in this section.