This is a pretty harrowing story for those that don't know. They were carrying atomic bomb secrets so they couldn't call for help. The crew floated around in water getting eaten by sharks. The old man in Jaws does a good job of telling the story. You should definitely research it if you are interested in that sort of thing.
If you read the relevant part of the Wikipedia article, that's not actually true:
> In the first official statement, the Navy said that distress calls "were keyed by radio operators and possibly were actually transmitted" but that "no evidence has been developed that any distress message from the ship was received by any ship, aircraft or shore station."[22] Declassified records later showed that three stations received the signals; however, none acted upon the call. One commander was drunk, another had ordered his men not to disturb him and a third thought it was a Japanese trap.[23]
It looks like nobody noticing the sinking until a plane saw the survivors floating in the water was not due to any secrecy requirements, but rather due to four people screwing up simultaneously (the fourth being Lieutenant Stuart Gibson, who didn't notify anyone when he noticed the ship was overdue).
A big part of the silence is that circumstances of the sinking is that it would challenge the perception of the Navy and military in general.
It's an amazing feat that the wartime was able to run as well and successfully as it did. That said, there were plenty of idiots, drunks and dysfunction all over the place.
Major Winters of the Band of Brothers fame was originally in the army as an enlisted man. But while in basic training he witnessed an army officer giving a presentation while holding a wrong rifle for an hour. So he realized maybe being an officer would not be so hard after all and applied to be an officer. The rest is history.
Had to look at the Wikipedia page under etymology. I got the gist at least. They didn't want to call it a land cruiser or landship due to secrecy, so were trying to bill it as a machine for carrying water. Water Carrier would give their committee the same initials as essentially the British word for toilet, so they changed it to tank supply as in water tank.
https://en.wikipedia.org/wiki/USS_Indianapolis_(CA-35)
Bataan Death March, Rape of Nanking, most of WWI, all pretty gruesome and what humanity is capable of pretty quickly.