Get a disposable water camera and get in the tub (or pool) with your little one and take splashy photos. You can take underwater pictures of their cute feet! We just did this, but haven’t gotten any photos developed so I’m not sure yet how successful it’ll be.
If you’re a digital photo household, don’t let these pictures sit around forever, sites like KodakGallery.com will accept your film and convert it to digital. I think you can even do it at Walgreens.