I saw this earlier today – Happy Submarine Month 2021
April is definitely submarine month in the United States. It’s also been that way for me personally since it was the month that my most memorable submarine experience celebrates an anniversary. The USS San Francisco SSN 711 was commissioned in April 1981 which was forty years ago. She has now been reborn as a Moored Training Ship and will begin her new service soon.
https://theleansubmariner.com/2021/04/03/happy-submarine-month-2021/