The expedition is expected to last until next Thursday.
Bressie's stepping out of his comfort zone and in to a kayak to help raise funds for his charity, Lust for Life.
The Blizzards front-man and mental health advocate is paddling the entire length of the Shannon with his friend Ray Carolan of Lakeland Kayaks.
The expedition starts at the river's source in Dowra, Cavan and will take them through Athlone, all the way to Limerick next Thursday.
6 foot 6 Bressie says he had some reservations about the mode of transport:
Catch the full interview with Bressie on Health & Fitness with David Hollywood from 7pm.