I think the source for the Morse code request is from FIRST students who will be entering the
underwater robot contest, NURC, in June. One of the
tasks is to decode a repeating 5 words per minute, 3 letter airport code (eg PHX PHX PHX...). The speaker is approximately 12 feet underwater, at night, and is one of many taks that the teams can earn points.
4. You must activate the origin beacon button which will be lighted due to the system being armed and waterproof. The button will also be labeled to aid in finding it. Once the button is pressed, a Morse code tone will begin repeating a three letter airport set of initials to indicate the airport of origin. An underwater speaker will be located on the dashboard of the cockpit near the activation button of the origin beacon.
There are many strategies to "hear" and decode 5 wpm Morse underwater. It will be interesting.