The saltiness of ocean water can be attributed to the minerals and salts deposited by the various rivers that flow into it. However, rivers are not saline because:

Rivers stay fresh because their water is constantly replenished by rain, flushing dissolved salts onward toward the sea.

Salts do not simply settle out at the river bed, so precipitation at the bottom is not the reason.

Aquatic plants take up only tiny amounts of minerals and cannot account for keeping rivers unsalted.

River mud does not chemically neutralise salts, so that explanation is incorrect.

Because water keeps flowing, dissolved salts never accumulate in the river as they do in the ocean.

The ocean turns salty since it has no outflow, so salts brought by rivers concentrate there over time.