Portarthur, Derrybeg is classified as achieving Excellent Water Quality in 2025 based on the assessment of bacteriological results for the period 2022 to 2025. Portarthur, Derrybeg achieved an Excellent Water Quality rating in 2023 and 2024 and a Good Water Quality rating in 2022. 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.

Portarthur beach is a north facing, long sandy beach; confined by a rocky outcrop east of Inishmeane Island to the North and a small estuary to the south. Fixed dunes are frequent throughout the site. They support a wide variety of plant species including some rare plant forms. There are also a wide range of bird species. Portarthur is situated in a Gaeltacht area with a variety of islands off the coast. Activities at Portarthur beach include swimming, kayaking, boating, sailing, power boating, jet skiing, diving and other land based activities on the beach. The designated bathing area is approx. 0.225km2 and the extent along the water is approximately is 1070m. There is a deep gradient off Portarthur Beach with the water depth reaching 1m approx. 10m from the water line and continuing out at a deep slope.