The correct answer is: If the Soviets snuck past U.S. ships, then the two countries would be at war.
The naval quarantine (or blockade) of Cuba during the Cuban Missile Crisis in 1962 was a critical moment in the tense standoff between the United States and the Soviet Union. It was aimed at preventing further Soviet shipments of missiles to Cuba and was a response to the discovery of Soviet missiles already stationed there. The naval quarantine was significant because it heightened the risk of military confrontation and potential war if any ships attempted to breach the blockade.