Sylph and her class were originally planned to have sixteen 6-pound long guns, but the Admiralty Order of 22 April also established the ships with carronades instead.

[5] The brigs immediately attempted to escape and were chased by Sylph and Pegasus while Phoenix pursued the frigate, Leopard being too slow to assist.

[5] After a battle of twenty minutes Argo surrendered to Phoenix, while De Grier and Echo were driven ashore and Mercury, despite throwing fourteen of her sixteen guns overboard to lose weight, taken by Sylph.

[9][10][11] The two corvettes were able to use their speed to escape the squadron, but Calliope was not able to follow them and instead chose to cut away her masts and run herself on shore at 2:20 A.M. so as to not be taken by the British.

[13] After around forty-five minutes of firing, Sylph cut her cable and stood out from the river mouth having had one master's mate and two seamen killed.

[4][1] On 16 September a French expedition commanded by Jean-Baptiste-François Bompart consisting of the ship of the line Hoche, eight frigates, a schooner, and 3,000 soldiers, left Brest to sail for Ireland as reinforcements to the invasion of General Jean Humbert.

[18][17] The warning provided by Sylph and the squadron allowed the Royal Navy to bring together a force to attack Bompart's ships, resulting in the Battle of Tory Island on 12 October and a series of follow-up actions which saw Hoche and five of the frigates captured.

[1] This Spanish squadron had sailed from Brest at the end of May and was cornered by the fleet of Lord Bridport on 4 June, at which point they retired to the fortified port of Île-d'Aix.

[21] Bridport left a blockading force commanded by Rear-Admiral Charles Morice Pole of six ships of the line, three bomb vessels, four frigates, and Sylph, off the island.

[22] However, the Spaniards were protected by two forts on land as well as a floating battery of mortars, which Sylph reported to Pole had a much higher range than the British ships.

[22][23] At 3 P.M. a number of Spanish gun boats advanced and opened fire on them, forcing by 4:30 P.M. the British ships to cease their bombardment and sail out of range of the Spaniards.

[25] Sylph continued to patrol the northern coast of Spain and the Channel in 1800-1; she fought two actions with unidentified ships off Santander on 31 July and 28 September of the latter year.

[28] After the combat she was filling with 1 foot 6 inches (0.5 m) of water an hour but managed to reach the Channel Fleet from where she was ordered by Admiral William Cornwallis to go to Plymouth for repairs, which she did on 14 August.

[25][29] Having been repaired, Sylph resumed her station off the coast of north Spain, and on 28 September discovered a French frigate of the same force as her earlier adversary.

[29] At 7:30 P.M. the two ships engaged each other from extremely close distance, exchanging broadsides for two hours and five minutes before the frigate disengaged, leaving Sylph with heavy damage to her rigging but again with minimal casualties, only one man injured.