This is one I have in grow out now too. It's about 4" now when I got it it was 1" maybe less smallest del I've ever seen. But all my dels have hung out near the top pretty sure it's natural. I'm guessing in nature they hunt bugs and small amphibians near the surface. They probably do this in the shallows as to protect themselves from larger predators, and like said above they do breath air also. Mine is very comfortable near the surface. I have taken advantage of this to start hand feeding it and getting it used to interacting with me.