These reclaimed lands are now wetlands associated with wildlife conservation and birdwatching, and support over 4,000 whooper swans and thousands of Greenland white front, barnacle, greylag and brent geese.

[citation needed] The lough is known for its wildlife-watching (dolphins, porpoise, seabirds, migratory geese and swans) and diving on a number of ship wrecks,[1] including SS Laurentic sunk by a German mine (possible torpedo), which went down with 3,211 ingots of gold of which 3,191 were recovered.

[10] The lough, and the Grianán Ailigh hill fort (early fortification and palace dating from 2000 to 5000 BC) at its southeastern bend, were recorded on Ptolemy's map of the world.

In October 1798, immediately prior to the outbreak of the Napoleonic wars, a French fleet carrying Wolfe Tone of the United Irishmen, plus troops to assist in 1798 rebellion, was intercepted and defeated in a naval battle at the entrance to Lough Swilly.

[15] A subsequent reassessment of the threat of invasion led to the building of a series of fortifications guarding the different approaches and landing points within the lough which were completed between 1800 and 1820.

On one occasion in this period, a Royal Navy ship entered the lough and – while it did not initially respond to signals that it should turn back – left the area without any action being taken.