Elephants have unique sphincter-like muscles in their ears. These valves close their ear canals, so avoiding water ingress while swimming – err, yes, elephants are excellent swimmers.
This also creates sealed acoustic tubes which work with fat and aerated bones in the skull to amplify infrasonic (low frequency) signals. Perhaps they are enjoying the songs of whales or the erudition of dugongs.
The new novel Padma and the Elephant Sutra can be downloaded Here
Sketch by Francesca Lindsay-White