Keenan, 39 and from Dublin, had been a freediver for eight years, working in the Philippines and Spain as well as Egypt, and had set Irish national records.

An AIDA Instructor Trainer and PADI and SSI Freediving Instructor, he was an experienced support diver, having held supervisory roles at international events including Vertical Blue and the World Depth Championships.

Keenan was reported to have provided assistance to Italian freediver Alessia Zecchini after she became disorientated while attempting to dive the arch, which is more than 25m from side to side and lies at a depth of almost 60m.

She made it to safety but Keenan apparently suffered a black-out before reaching the surface.

Ireland's Department of Foreign Affairs was reported to be providing consular assistance to Keenan's family.

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