The weird origins of going to the beach [washingtonpost.com]
"But a deep cultural appreciation of the benefits of being at the beach really started in England in the late 18th and early 19th centuries, largely because of medical prescriptions at the time. Many contemporary doctors believed that bathing in cold sea waves was beneficial for conditions they called "melancholy" and "spleen" - an excess of black bile that made people introverted, depressed, cautious or moody."
Probably from the category "things you never really thought about but are kinda interesting anyways".