magnetism doesn't just affect ferrous objects, but do reach this point takes tremendously powerful magnetic fields.
i've read in a popular science (cannot remember which one or when) about a research team levitating a spider with an enourmous electromagnet. i'm gonna try and find an article or pics.
edit: ahh,
here's a page. so hard to find, i had to consult luelinks.net, but luelinks seems to have a link to anywhere on the web, so it only took one search
edit 2: and
here's another page with more information on the subject, including what appears to be (at first glance) formulas.
edit 3: and finally, a rough enough explanation to tell how the frog, water, etc. was levitated and to explain how any object can be influenced by powerful magnetic fields.
In fact, it is possible to levitate magnetically every material and every living creature on the earth due to the always present molecular magnetism. The molecular magnetism is very weak (millions times weaker than ferromagnetism) and usually remains unnoticed in everyday life, thereby producing the wrong impression that materials around us are mainly nonmagnetic. But they are all magnetic. It is just that magnetic fields required to levitate all these "nonmagnetic" materials have to be approximately 100 times larger than for the case of, say, superconductors.
and for all it's worth while we're on the subject of magnetism, your eye's are slightly magnetically charged. the front (where the pupil is) is slightly negative, and the complete opoosite side of the eye to the pupil is slightly posotively charged. probably not enough to be affected by everyday magnets, but enough to drive development behind a computer interface device that uses movement from the eyes to place a cursor on the screen.