Rusticle

right|thumb|Detached rusticles below port side anchor of the Titanic|RMS Titanic A rusticle is a formation of rust similar to an icicle or stalactite in appearance that occurs deep underwater when iron-eating bacteria attack and oxidize wrought iron and steel. They are seen on underwater photographs of shipwrecks, such as the RMS Titanic and the German battleship Bismarck. They have also been found in the #3 8-inch gun turret on the stern of the USS Indianapolis. The word rusticle is a portmanteau of the words rust and icicle and was coined by Robert Ballard, who first observed them on the wr