With the end of the
Peace of Amiens in 1803 Dundas returned to sea in 1804 in command of the 36-gun
fifth rate . He was initially assigned to patrol off the west coast of Spain and in the
English Channel, where he captured several prizes. In mid-August 1805 Dundas had a narrow escape when he came across a large fleet off northern Spain, which challenged the
Naiad using British codes. This was in fact the combined fleet under
Pierre-Charles Villeneuve, heading for
Ferrol.
Naiad managed to escape, evading fire from the lead French frigates, and on 20 August Dundas fell in with Vice-Admiral Sir
Robert Calder's squadron, on its way to blockade Ferrol. Calder's force was then sent on to join the ships blockading the combined fleet in
Cádiz under Vice-Admiral
Cuthbert Collingwood, and Dundas used his time here to harass enemy supply ships. With the arrival on 28 September of Vice-Admiral
Horatio Nelson to take command of the fleet, the main British force withdrew over the horizon. Nelson deployed his frigates, including Dundas's
Naiad, and several ships of the line to provide a line by which the enemy fleet could be observed and signals transmitted back to him. When the combined fleet put to sea on 19 October
Naiad was third in the line, between the frigate and the 74-gun
third rate . As the combined fleet approached the British over the next couple of days,
Naiad and the other frigates shadowed it, reporting on its movements. ==Nelson and Trafalgar==