The Sora (Porzana carolina) is a small (Robin-Sized) rail that has a wonderful, descending "whinny" which can be heard mornings and evenings around marshes. Good luck catching a glimpse of this one, though, as they're normally secretive and inhabit the thick cattails and reeds. This one was recorded in Tavasci Marsh [Arizona]. Though they normally walk on the reeds and weeds or in shallow water, I have seen Soras swim briefly, too.