The lyrics were written by author and poet Jim Carroll (The Basketball Diaries). Most likely Carroll heard a radio program about Cousteau talking about:
In the episode "The Smile of the Walrus" (from the program 'Undersea World of Jacques Cousteau'. - November 1972. - ABC.) Cousteau talks about a sound that walruses make when produce bell sounds using air bags they have in their throats.
*Cousteau, Jacques. - The Ocean World of Jacques Cousteau: Invisible Messages. - Danbury Press. - 1973. - Page 70.
*Cousteau, Jacques; Philippe Diolé. - Diving Companions: Sea Lion, Elephant Seal, Walrus. - A&W. - 1974. Page 227.
*"Mammal Sounds". - QUOTE: "Their underwater sounds include teeth clacking and a bell or gonging sound ... a sound produced by forcing air through their trunks." - http://www.junglewalk.com/sound/mammal-sounds-P9.htm