Why Spanish marines are naval soldiers

How are Spanish marine ranks described within the naval service?

They are treated as soldiers, with soldado de marina meaning naval soldier.

A viewer asks how Spanish marine ranks fit into the naval system. Spanish marines are normally treated as soldiers rather than as another set of seagoing sailor grades. Soldado de marina is rendered as "naval soldier." The phrase makes the marine's soldierly function explicit while locating that force within the navy.