Mine are the same (: Not the waving part, but they do enjoy watching us! Even if we're not talking to them at the moment they use to be hovering in front of the glass, staring at us xD (I'm talking to my fish every day <3 telling them how much I love them and how beautiful they are<3) Our aquarium is just next to the couch, so they can see us whenever they want.
Once my fiance was asking if my fish understand what we're saying to them, or something similar, I can't quite remember exactly what it was... but then I said "Of course they do! Cream, tell him!" and then our white goldfish started moving her mouth really rapidly and seemed excited to tell him something
She's always like that, very talkative one.
The wonderful thing about these goldfish of mine is that they have such distinguished personalities! One is very, very cuddly (Cream) she's the first one rushing to the glass when we come home (: Second one is a strange fish, he's usually busy with exploring things, curious! (Hunny) and then finally, there's Fläckis (=Spotty) who's the silent one, seems a bit shy to show that he likes us
I feel a bit like a psycho for talking about this kind of things... xD