I think learning just the SOS distress signal (...---...) has a decent bang-for-buck ratio. And because of its frequent use in films there's usually not even much learning involved.
Although I don't know how true this is, I've tried to keep to this in other interfaces, avoiding three-blink patters on lights when someone is not in trouble.
There's a General Alarm signal (above), but no Abandon Ship signal. The captain gives those manually.
(I may be blatantly wrong!)
The General Alarm typically calls for the crew to proceed (at haste!) to the muster station to be informed of the nature of the emergency and be put to work handling the situation.
Luckily, I've only ever had to abandon ship during a couple of drills.
And the sign on the inside of your trunk / boot is a triangle.
Just be alert. The world needs more lerts.
Woah I had no idea!
https://www.youtube.com/watch?v=KVooUKtV3nQ
For those that don't want to click, it's a commercial for a brand of dish cleaner named S.O.S. There are dirty pots and pans that clang out the S O S message in Morse code, with subtitles spelling out the letters as they come out. A screen appears at the end asking "are your dirty pots trying to tell you something?"