It might be this (found in this Index of Feats PDF
Feat: Aquatic Fey Bloodline [Bloodline]
Source: (Dragon Magazine issue 335 p93)
Prerequisites:Able to cast Impromptu Arcane spells; Able to summon a Familiar
You are descended from a Siren, Selkie, Kelpie, etc.
1. You cannot learn spells from the Conjuration (creation) or Conjuraiton (healing) subschools. These
spells are removed from your spell list.
2. Add the following to your Known spells:
1. Charm Person 4. Charm Monster 7. Control Weather
2. Alter Self 5. Mind Fog 8. Horrid Wilting
3. Water Breathing 6. Control Water 9. Shapechanger