aletear

aletear
ah-leh-teh-ahr'
to flutter; to flap one's wings/fins
Examples
1. El colibrí aletea tan rápido que parece que ni se mueve.
The hummingbird flutters so quickly that it looks like it's not even moving.
 
2. El pez aleteaba casi como si me estuviera saludando.
The fish flapped its fins almost as if it were waving at me.