Some caterpillars can breathe underwater

Unlike other amphibious creatures that can survive underwater on stored oxygen but must come back up for air, these caterpillars can spend several weeks without ever breaking the surface...

It isn't yet clear how the insects do it. Rubinoff and co-worker Patrick Schmitz of the University of Hawaii did not find any water-blocking stopper over the caterpillars' tracheae or evidence of gills. The animals drowned quickly when kept in standing water, so they seem to need the higher levels of oxygen present in running water, and probably absorb it directly through pores in their body...