The reason the ocean tastes salty is because piss and shit has sodium in it.
The ocean tastes salty because it's full of fish and piss shit
The ocean is a giant communal sewer
Lakes and rivers have mammals and birds eating the fish, and those mammals don't crap in the water, because they drink it, so they're a lot less salty
But the ocean is just a bunch of fish eating each other and plants and then shitting each other back out into the ocean
That's why mammal crap floats, but fish poop just dissolves, it's already more or less liquid, they don't really chew that much.
Maybe someday fish will evolve to have super-powerful bowel systems, so that they can breach the surface, and then shit so hard the crap flies off into space, so it stays out of the ocean, and the ocean can be clean again.
Like the Dolphins in Hitchhiker's Guide to the Galaxy
