Soon afterwards he joined the Trident, the ship of Rear-admiral Sir Peter Denis; subsequently went a voyage to Nevis in the West Indies, and in December 1775 became surgeon to the sloop Hazard.
He very soon exchanged into the Surprise, commanded by Captain Robert Linzee, which reached Quebec in May 1776, and thence accompanied Admiral Montagu's squadron to St. John's, Newfoundland.
In 1778, in which year he says he published a volume of Remarks on the Earl of Chesterfield's Letters, he was transferred to the Conquistador, which was stationed at the Nore for the reception and distribution of impressed men and volunteers.
Rymer, who attributed his transference to the dislike of his commanding officer, wrote a somewhat scurrilous pamphlet under the title Transplantation, or Poor Crocus pluckt up by the Root, 1779.
In 1828 he published A Treatise on Diet and Regimen, to which are added a Nosological Table, or Medical Chest Directory, Prescriptions, &c., 1828, 8vo, which he dedicated to John Abernethy.