Salt is a solute.
In other words, the substance that is being dissolved is called a solute and the substance that does the dissolving is called the solvent.
For a given solution, a quick way to identify the solute and the solvent is by looking at the amounts of each component of the solution. The substance that is present in the largest amount will be your solvent and the substance that is present in the smaller amount will be your solute.
In the case of ocean water, you have much, much more water than salt, which means that water will be your solvent and salt will be your solute.