Back when I did my CPL in the UK we had to be fluent in receiving morse.
It was about as useful in my life as an instructor as the Decca and Omega navigation systems we had to learn.
I learned it from a tape, would have practised on car numberplates but lived in Jersey so I knew .--- really well.
I remember learning mnemonics like "elephants in straw hats ten miles off" . .. ... .... - -- --- , fetch a fireman ..-. god save the queen --.- beethovens 5th for v ...- etc etc but still get stuck on some of them!