Man, everyone's concepts are amazing!
I love how graceful the sea-to-sky creatures are. I may have chosen to do something... a tad more unusual. I hope this doesn't qualify as going overboard... heh. I have never drawn hippos before, but they have pretty awesome dinosaur feet. I was just playing around tonight - some quick hippo sketches.
I like the idea of something so large and cumbersome allowed to take flight. I am still considering the mechanized portion, and the type of flying apparatus. But... hippo sketches!