Flying
At the beginning of your upkeep, return an enchantment you control to its owner's hand.
If Riptide Chimera is the only enchantment you control when its ability resolves, you must return it to its owner's hand.
If you control no enchantments when Riptide Chimera's ability resolves (perhaps because Riptide Chimera stops being an enchantment for some reason), then nothing happens.