Duncannon is classified as achieving Excellent Water Quality in 2025 based on the assessment of bacteriological results for the period 2022 to 2025. Duncannon has achieved a Good Water Quality rating in 2024 and Sufficient Water Quality rating for two years 2022 and 2023. Annual water quality ratings are generally calculated using monitoring results over a four-year period and are assessed against stringent bacterial limits to protect bather health.

Duncannon beach is a peaceful firm-sand beach with a relatively gentle slope. The sand dunes extend between 5m and 100m to the rear (north) of the beach. There is no significant vegetation growing in the waters off the beach. Wild Sage (Salvia verbenaca), a rare species listed in the Irish Red Data Book is found in the dunes. There is a sand sculpting festival which takes place each summer. Attractions include a maritime museum, cockleshell art centre, artist studios, café and craft shop. The beach is also used by a limited number of surfers, windsurfers and canoeists. The bathing area is approximately 1.0 km long and approximately 0.2 km² in area.