I think you did smashingly well on this build. The AT-AT swimmer became an instant favorite of mine when I saw it on Mon Calamari in the Legacy comics. I think your rendition of the "leg" discs is impressive.
Not a big fan of lego star wars stuff (cause there are soo many) but this really caught my attention. The shape and use of parts are phenominal. My only comment would be that it may look a bit nicer if you covered it with flat tiles so that it was smooth. Nice job anyways!