Mark O’Donoghue and his partner are ambling along their local beach. It’s a familiar Floridian scene – waves lapping at the shore, footsteps imprinting into the soft earth. Then a strange structure coming out of the ground stops the couple dead in their tracks. The duo have discovered some sort of curious contraption, all jagged wood and metal. And in a remarkable stroke of luck, it’s just re-emerged after centuries concealed beneath the sand.