Designed by Ben Lexcen, built by Stephan Ward, owned by Alan Bond and helmed by John Bertrand, the Australia II featured an innovative winged keel design developed by Lexcen. This helped to make it very fast and maneuverable in many conditions and was the most notable and controversial design feature of the boat. During the summer of 1983, as selection trials took place for the Cup defense that autumn, it was unclear whether the keel design was legal within the strict rules governing the 12-meter class.

Questions also surrounded the Dutch involvement in the design of the keel, which under the rules had to be designed by an Australian. The keel design was eventually confirmed as legal while the keel origin controversy remains unanswered. Despite being the first 12-meter to sport the new design, Australia II was not the first boat to have a winged keel, though her success did much to make the concept popular.

The Atlantic was built in 1903 by Townsend and Downey shipyard, and designed by William Gardner, for Wilson Marshall. The three-masted schooner was skippered by Charlie Barr and it set the record for fastest transatlantic passage by a monohull in the 1905 Kaiser's Cup race. The record remained unbroken for nearly 100 years.