The crossword solution for the term 'Shark Rival' is 'JET', which is a three-letter word. JET is a type of aircraft that is powered by JET engines, which are engines that use a JET of hot exhaust gases to propel the aircraft forward. Jets are typically faster than propeller-driven aircraft and are used for both commercial and military purposes. In the context of the term 'Shark Rival', jets could be seen as rivals to sharks in terms of speed and maneuverability.