Regarding the Suez Canal - Blockade

Cuban Missile Crisis

The U.S. Navy played a pivotal role in this crisis, demonstrating the critical importance of naval forces to the national defense. The Navy, in cooperation with the other U.S. armed forces and allies, strategically employed military power in such a way that the President did not have to resort to war to protect vital Western interests. Khrushchev realized that his missile and bomber forces were no match for the Navy's powerful Polaris missile-firing submarines and the Air Force's land-based nuclear delivery systems once they became fully operational. Naval forces under the U.S. Atlantic Command, headed by Admiral Robert L. Dennison, steamed out to sea, intercepting both merchant shipping enroute to Cuba and Soviet submarines operating in the area. U.S. destroyers and frigates, kept on station through underway replenishment by oilers and stores ships, maintained a month-long naval quarantine of the island. Radar picket ships, supported by Navy fighters and airborne early warning planes, assisted the Air Force's Air Defense Command in preparing to defend American airspace from Soviet and Cuban forces. Playing a vital role, Navy aerial photographic and patrol aircraft observed the deployment of Soviet offensive weapons into Cuba

Two by sea?

(and eventually monitored their withdrawal by sea).

https://www.history.navy.mil/browse-by-topic/wars-conflicts-and-operations/cuban-missile.html

The words used by Henry Wadsworth Longfellow in his poem “Paul Revere's Ride” to describe the signal used to guide the “midnight ride of Paul Revere” at the start of the Revolutionary War. Revere had ordered two lanterns to be placed in a Boston church tower to warn his confederates that the British were on the move. Longfellow embellished the story a little.

https://www.dictionary.com/browse/one-if-by-land–and-two-if-by-sea