‘’Keep your arms across your chest!” commanded our guide. “Legs together!” We snapped into the vampiric pose obediently. “Oh, and don’t forget to scream…”

This was our briefing. We stood, suited and booted in heavy wetsuits and helmets, and were considered ready. In silence we edged towards the edge of the small rock pool we were standing in. One of our guides went first, leading by example. He stood on the precipice, threw us a quick smile, and then he disappeared.