That brown, muddy water is due to a large algae bloom, expanding from the Santa Monica pier all the way to Marina del Rey.
"We don't have blooms this intense that often," said UCLA Associate Adjunct Professor Dr. Rebecca Shipe. "It's a naturally occurring event, happens sometimes. It's very exciting because it's just so beautiful.
Shipe has been studying algae blooms for more than 20 years and says one this large occurs when that species of algae has the perfect conditions.
"High nutrients, lots of sunlight and for some reason, they're trapped in a pool of water," she said.
As the algae decays, it uses up oxygen in the water, which, depending on the environment, can be a concern for local wildlife. Shipe said in this case, that's nothing to worry about.
"That's more of a problem in a harbor or marina where fish are trapped, but if you look at this bloom, fish can swim out," she said.
While algae blooms are not directly toxic to humans, they can sometimes cause allergic reactions, so experts recommend safely observing them from land.
The best time to observe the blooms are at night when they're bioluminescent.