Intended for a career at sea, Plampin joined the Navy in 1775, aged 13, and served aboard HMS Renown under Captain Francis Banks off the coast of North America during the American Revolutionary War.

In Sandwich Plampin participated in the Battle of Martinique in April 1780, and subsequent operations, earning a promotion to lieutenant aboard HMS Grafton and returning to Britain.

Parker was impressed by his subordinate's language skills and intelligence and, in 1793, suggested Plampin for a mission to the Netherlands, at that time allied to Britain in the French Revolutionary Wars.

[1] Plampin assumed command of a flotilla of gunboats based in the Dutch harbour of Willemstad, then under siege by a French army under General Charles François Dumouriez.

Plampin subsequently became a lieutenant in HMS Princess Royal and sailed for the Mediterranean, joining the British fleet assisting the Royalist forces at the Siege of Toulon.

[1] In August 1793, Plampin was given command of the hired armed sloop Albion, which he paid off on 11 September 1794, and then the floating battery Firm, operating off the Scheldt and the Dutch coast.

[2] Arriving in the Indian Ocean, Plampin found no sign of Willaumez (who had remained in the Atlantic), but did discover that British trade was under constant attack from French frigates and privateers based on Île de France, which particularly targeted the large East Indiamen.

Disguising Powerful as an East Indiaman, Plampin cruised off Ceylon in search of the enemy and on 9 July discovered Bellone under pursuit by the Royal Navy sloop HMS Rattlesnake.

[4] Part of Plampin's duties was to observe the former French Emperor Napoleon Bonaparte, who was kept prisoner in a house on the island of Saint Helena, deep in the Atlantic Ocean.

[1] On his return to Britain in September 1820, Plampin applied to become a Knight Commander of the Order of the Bath, but was informed by Lord Melville that such awards could only be made for service in the face of the enemy.