Around 14,500 years ago, at the end of the last ice age, the collapse of a large chunk of ice, likely from the Laurentide Ice Sheet covering North America, initiated an event known as Meltwater Pulse 1A. Sea levels rose more than a foot—and more than a mile of coast disappeared—per decade, displacing those living near shorelines. The earth’s human population was then roughly three million, 0.04 percent of what it is today.

“Waters from snow and ice are all bad,” opined Hippocrates of Cos around 400 bc. “Once frozen, water never recovers its original nature, but the clear, light, sweet part is separated out and disappears.” Such melted waters, he declared, “are the worst for all purposes.”

In 1967 Bobby and Ethel Kennedy participated in the tenth annual Hudson River Whitewater Derby. Bobby’s kayak capsized in the freezing water; he was hurtled down the rapids. The next day Ethel attempted the course, accompanied by a ski expert and a mountain guide; the trio’s canoe tipped over three times. “A rescue party’s been sent up the river to get Mrs. Kennedy, who is on a rock,” an announcer told those waiting at the finish. “She’s having a bad day.”

A 2018 study of sediment cores taken from the bed of Walden Pond found signs of “cultural eutrophication”: human urine released into the pond since it became a popular swimming spot in the 1920s has altered the water chemistry and could turn the “beautiful clear lake into a slimy green stew.” The study was reported in the Boston Globe with the headline “Please Stop Peeing in Walden Pond, Researchers Beg.”

Thirteenth-century Japanese Buddhist Mugai Nyodai, the world’s first Zen abbess, struggled to achieve enlightenment until, one night during her training, the bottom fell out of an old bamboo-bound pail she was using to carry water. The spill freed her. “No more water in the pail!” she wrote in a poem commemorating the experience. “No more moon in the water!”