The first test would probably be a ground burst, but consideration was also given to an explosion in a ship to measure the effect of a ship-borne atomic bomb on a major port. Such data would complement that obtained about an underwater explosion by the American Operation Crossroads nuclear test in 1946, and would therefore be of value to the Americans. Seven Canadian sites were assessed, the most promising being Churchill, Manitoba, but the waters were too shallow to allow ships to approach close to shore.