Sandy: Welcome to the forum! The depth of field is nice, as is the catch light in the eye. Personally, I like the salvinia on and around the grebe as it captures their habit and habitat; although, aesthetically, many here are likely to differ. The two problems I see are overall image softness (as you say, it is a large crop) and the hard shadow left of the subject. Keep shooting and posting!
Nice first post. I also like the habitat. As well as the other suggestions, getting as close as possible to eye level almost always improves a photo so lower if possible would have worked fine here.