Submarine Day takes place on March 17, 2021. Submarine Day celebrates the day that John Philip Holland, an Irish engineer, first successfully demonstrated his submarine called the Holland VI. On St. Patrick’s Day, 1898, ist made her first successful submerged run which impressed observers by the US Navy Department. John Philip Holland designed submarines that, for the first time, made use of internal combustion engines on the surface and electric battery power submerged.
The Assistant Secretary of the Navy, Theodore Roosevelt, recommended to buy the Holland VI. Several months later, it was the Navy's first submarine, which was later named the USS Holland (SS-1). By the way: the National Submarine Day, which commemorates the purchase of USS Holland (SS-1), takes place one month later in April.
A submarine is a watercraft capable of independent operation underwater. Although experimental submarines had been built before, submarine design took off during the 19th century, and they were adopted by several navies. Submarines were first widely used during World War I (1914–1918), and now figure in many large navies.
Today, Submarines have one of the widest ranges of types and capabilities of any vessel. They range from small autonomous examples and one or two-person vessels that operate for a few hours, to vessels that can remain submerged for six months - such as the Russian Typhoon class, the biggest submarines ever built. Submarines can work at greater depths than are survivable or practical for human divers. (With material from: Wikipedia)