what is it?

it is halfway between saltwater and freshwater. Water with some salt in it but no as much as marine.

Well, not just halfway but anywhere in between. In nature the gradient is usually pretty gradual. I live on Charlotte Harbor, which has a brackish zone of probably twenty miles right now and thirty during the rainy season.

Brackish water occurs where fresh water meets marine water. The two mix and create an enivironment that is part marine salts and part freshwater. The further you go away from the fresh water source, the more marine the water becomes.

Just note that brackish water is not water with salt in it. It has to have marine salt in it.

BTW, that is *not* a stupid question. Most people don't even ask and put brackish water fish in water treated with aquarium salts. The fish die and they have no idea why. So, your question is extremely valid and I'm really glad you asked.

Roan