National Sea Monkey Day is observed on May 16, 2021. Sea-Monkeys is a brand name for brine shrimp - a group of crustaceans that undergo cryptobiosis - often sold in hatching kits as novelty aquarium pets. Invented in 1957 by Harold von Braunhut, the product was heavily marketed, especially in comic books, and remains a presence in popular culture. Initially called "Instant Life", von Braunhut changed the name to "Sea-Monkeys" in 1962. This was based on the supposed resemblance of the animals' tails to those of monkeys, and their salt-water habitat. The product was intensively marketed in comic books.
The colony is started by adding the contents of a packet labelled "Water Purifier" to a tank of water. This packet contains salt and some brine shrimp eggs. After 24 hours, this is augmented with the contents of a packet labelled "Instant Life Eggs", containing eggs, yeast, borax, soda, salt, and sometimes a dye. The animals which hatched from the eggs over the previous day seem to appear instantly. "Growth Food", containing yeast and spirulina is then added every few days. (With material from: Wikipedia)