Killahoey is classified as achieving Excellent Water Quality in 2025 based on the assessment of bacteriological results for the period 2022 to 2025. Killahoey has achieved an Excellent Water Quality rating for the four consecutive years 2022 to 2025. 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.

Killahoey beach consists of a sandy beach with a large inflowing estuary including a large mud flat at the east of the beach. These are exposed at times during the tidal phase during the day. Killahoey beach is a diverse coastal site containing a wide range of habitats from high rocky quartzite cliffs in the north to mud flats, sand flats, dunes and a brackish lake in the south. These different habitats support a wide variety of wildlife and plant species. Killahoey beach is a proposed NHA (National Heritage Area). It is also part of a Special Area of Conservation (SAC). Activities at Killahoey beach include swimming, kayaking, boating, windsurfing and other land-based activities such as football, horse riding, kite flying, etc. The bathing area is designated and is approx. 0.6707km2 and the extent along the water is approximately is 1570m. The depth of the water on the shoreline increases within 2 meters off the shore to a depth of 1 meter and gradually increases to greater than 2 meters with the slope of the shore.