George was born on 8 September 1758, the son of Thomas Ryves, of a long-established Dorset family, by his second wife, Anna Maria, daughter of Daniel Graham.

In April 1775 he joined HMS Portland, going out to the West Indies as flagship of Vice-Admiral James Young, and shortly after arriving on the station was appointed to command the tender Tartar, carrying eight guns and a crew of thirty-three men.

In her he returned to England in 1782, and early in 1783 he was appointed to HMS Grafton, which sailed for the East Indies; but, having been dismasted in a gale in the Bay of Biscay, was obliged to put back and, consequent on the peace, was paid off and Ryves placed on half-pay.

On arriving at St. Lucia, in the absence of the Bulldog, Ryves volunteered for service with the seamen landed under the command of Sir Hugh Cloberry Christian for the reduction of the island, and rendered important assistance in the making of roads and the transporting of heavy guns.

On 29 May 1798 he was advanced to post rank, and in April 1800 was appointed to the 64-gun HMS Agincourt, which during the summer carried the flag of Sir Charles Morice Pole on the Newfoundland Station.