I didn't see the show, but it sounds like they're talking about
defensins: antimicrobial peptides that are found in frog skin,
and presumable crocodile skin.
(actually, there pretty much everywhere, the current issue of
Am J Physiol Cell Physiol indicates similar compounds are found in
venoms (bee, scorpion, jumper ant, wolf spider)
skin secretions (frog, carp), and cells of the immune system)
Polymyxin-type antibiotics are also related to these compounds.
They act by forming holes in cells.
Basically, a bunch (6 or 12?) of these helical peptides assemble in
a lipid membrane to form a pore. Enough pores = cell death.
No crocodile tears,