"Hydra" was commissioned on 19 January 1839 under Commander Anthony William Milward to operate in the Mediterranean Sea. After Milward's death in early 1840 Commander Robert Spencer Robinson was appointed to her. "Hydra" then saw action during the Syrian War, as part of a squadron under the command of Commodore Charles Napier (the ships , , , , , frigate , and steamer ) operating off the coast of Ottoman Syria. In Admiral Sir Robert Stopford's report on the Anglo-Austrian-Turkish landings in September 1840 he noted that the steam vessels had been "eminently useful in constantly moving along a great extent of coast with troops and arms, and taking part in the attacks upon the different forts".