[intro music] Hank Green: Cobalt, cerulean, turquoise, teal.... We've all seen lakes (or at least pictures of lakes) best described by these shades of blue. If I say "green", you may think of a lake full of algae, and if I say "brown", perhaps you'd think of murky, gross-looking stained pond, but I doubt that you would associate pink with a body of water -- that is, unless you've recently flown over the southern coast of western Australia and happened to look out the window at the right moment and thought "what the heck is that‽" That would be Lake Hillier. Situated on Middle Island, the largest of 105 islands in the Recherche Archipelago, Lake Hillier is tiny in size (only about 600 by 250 meters) but it is grand in spirit because Lake Hillier is pink. Like, like really pink. Bubblegum, Pepto-Bismol, strawberry shake pink, like "eccentric billionaire just had twin baby girls and wants the world to know" pink. The color is not a trick of the light; the water retains its hue when removed from the lake and put into a container for, say, a cheap but cool Valentine's Day gift for your beau. And interestingly, scientists aren't totally sure why Lake Hillier is so rosy, but it's probably because it's about ten times saltier than the ocean, and thus the lake is chock full of salt-loving microalgae known as Dunaliella salina, one of the few organisms that has adapted to life in such incredibly salinous water. These little guys produce carotenoids, pigment compounds that absorb sunlight, like beta carotene, the same stuff found in carrots and purple cabbage, which range in color form yellow to red. This algae may be the leading candidate as the cause of the pinkness because there is another, very similar, pink lake in Senegal, Lake Retba, and it too is home to D. salina. The color of the lake is most intense during the dry season, when water levels drop and the salt content rises, and intense sunlight causes the algae to flourish. But there may also be another culprit. Halobacteria, which, despite their name, are not even bacteria but salt-obsessed members of the domain Archaea. See, the colored carotenoids in algae like D. salina (or possibly "sal-EE-na"; I may have been saying it wrong this whole time), they're found only in the chloroplasts, which the algae use to photosynthesize, but the halophilic Archaea keep their pigments dispersed throughout the whole cell like blushing schoolgirls, making them more readily visible. These halophilic microbes are true extremophiles and can hibernate in salt crusts for thousands -- perhaps millions -- of years. They are some of the oldest living organisms on Earth, and some scientists believe that if we someday find life on Mars, they may resemble these guys. They also may be one of the reasons why that fancy salt you bought at the organic food store is pink. Even if we don't know the exact reason why Lake Hillier is so flamboyantly fabulous, we do know that it is perfectly safe to swim in, making it the ultimate Barbie vacation destination. Thank you for watching this episode of SciShow. If you have any questions, comments, or suggestions for other weird places you'd like us to discuss scientifically, you can find us on Facebook or Twitter or down in the comments below, and if you'd like to keep getting smarter with us here at SciShow, you can go to youtube.com/scishow and subscribe. [outro music]