Mayo faces the Atlantic Ocean along a coastline that stretches from Belmullet in the north to Achill Island and Clare Island in the south. Sites range from sheltered shore entries such as Old Head and Elly Bay, suited to beginners, to deeper boat dives like Carraig Cois Ceim, which reaches thirty metres and requires settled summer weather for the best visibility. The water is cold year-round, peaking in late summer and dropping to its lowest in late winter, so a drysuit is the practical choice for most divers. Reef, kelp forest, wall, and seagrass habitats all feature, with species including gorgonian, whip coral, nudibranchs, pollack, and harbour seals encountered across the area.
Monthly water temperature across Mayo's sites, from satellite sea-surface data corrected for depth. The band shows the site-to-site spread.
Water temperatures are cold throughout the year, rising gradually from spring to a late-summer peak before falling again through autumn. Deeper, exposed sites such as Carraig Cois Ceim see their clearest conditions during settled summer weather, while sheltered sites like Old Head are accessible across a wider part of the year.
Water temperature around Mayo ranges from about 9°C in February to 16°C in August, based on satellite sea-temperature data for its dive sites.
In the warm season (about 16°C) a 7mm or semi-dry suit is comfortable in Mayo; in the coldest months (about 9°C) step up to a drysuit.
Fin maps 8 sites in Mayo (6 scuba diving sites and 5 snorkelling spots, with some suited to both).
7 more sites to explore
