The river Thaw (Dawan) flows into the sea at Aberthaw and Iolo included a poem to this river in Poems, Lyric and Pastoral (1794).
The port at Aberthaw is mentioned frequently in Iolo's papers despite the fact that it had deteriorated by the end of the 18th century. When he worked as a stonemason with his father Iolo would sail to Bristol from Aberthaw to buy marble, and he later followed the same route on his numerous visits to London. Indeed, for a short while at the beginning of the 1780s he owned a sloop called the Lion, which regularly crossed the river Severn from this small port.
At the beginning of 1781 Iolo made an unsuccessful application for the post of customs officer at Aberthaw. He was also interested in the port's history and his papers are full of documents and information which he gleaned from elderly locals.