Normally Korra's used to the surprise and incredulity that came after she showed someone her bending for the first time, but Annabeth's reaction actually surprised the Avatar instead.

"Yeah, any kind of water." As an example, she turned the water in the air into still ice. "You've seen something like waterbending before?" Her first immediate thought is Kaldur; he was the closest to being a bender that she had seen on the turtle.