Heat from the sun makes the water in the ocean evaporates but the salt stays in the ocean. When the ocean water evaporates it creates clouds then it makes rain but the rain water isn't salty from the ocean. All the salt stays on the ocean and the rain water is fresh. The salty water if heavier and what it does to the fresh water it pushes away and creates also a current.
Fishes that lives in the ocean needs currents to stay alive. The currents help them to move around so they wouldn't die. Also they need the current for food and oxygen. Also they need the currents to live linger and also it helps them to exercises to prevent fatty around their heart. So for fishes in the aquarium they what people do they uses vents, pups, and more to create that wave motion for fishes to be comfortable on their new habitat.
A current is a body of water or air moving in definite direction through a surrouding body for water or air in which there is less movement. A thermohaline currents is driven by global gradients created by surface heat and freshwater fluxes. Scientist uses data marker buoys. This buoys sends data to measure the surface of the ocean currents back to the scientist.
The Great Salt Lake and Dead Sea are salty because they don't have a way to go to the ocean and the mineral keeps the salt in the same place.