Final answer:
Proper conduct when boarding a ship with the National Ensign flying includes saluting the flag and requesting permission to come aboard, respecting both the symbol of the nation and naval tradition.
Step-by-step explanation:
When boarding a ship that is flying the National Ensign, proper conduct entails saluting the flag before boarding. This is a formal act of respect towards the nation's flag, which is emblematic of national pride and military etiquette. Additionally, it is customary to request permission to come aboard which is a traditional naval courtesy.
Here's the proper sequence of actions: First, approach the ship's quarterdeck and salute the flag. Then, request permission to come aboard from the officer of the deck. Once permission is granted, board the ship. If there is an officer on deck, it is also appropriate to salute that officer.