Continuity mistake: When Hugh O'Brian and Barbara Bouchet are driving up from the beach during the Japanese attack, they are in a Lincoln convertible. When the car explodes and goes over the cliff, it is either a Ford or Mercury convertible.
Continuity mistake: The same sailor calls General Quarters on Torres' Cruiser as well as the Cassidy while at Pearl Harbor. It was the same southern drawl sailor on the mic for both ships.
Continuity mistake: During the discussions right after the attack on Pearl, between CINCPAC and all the admirals over the plotting table, Dana Andrews is nowhere to be seen. Then after a quick cut away and back, suddenly he is there just to the right of CINCPAC with all the other actors magically rearranged to make a space for him.
Continuity mistake: In the first few scenes concerning Captain Torrey's task group, the weather is sunny and clear (as it was Dec. 7, 1941). However, at one point when Cmdr Eddington enters the bridge, he is in very wet foul weather gear, and the same when they go into the coding room to decode the message to "seek-out" the enemy. Later when steaming toward the enemy the weather is clear again.
Continuity mistake: After USS Cassidy joins Torrey's group, Mac is on the bridge conversing with another officer, and the "Swayback" is visible on the port quarter. A submarine contact is made at 020/2000 yards which would be even further to starboard, and the Cassidy prosecutes the contact. Then the "Swayback" gets hit with two torpedoes on the PORT side.
Answer: One Star rank wasn't formalized until 1943. Rear Admiral lower and upper wore the same 2-stars.