Monty takes a team of expert deep divers to Namibia in south-west Africa to explore a deadly sinkhole lake in the desert; their goal is to locate a safe reputed to contain £60 million worth of gold.

Monty and his team travel to a remote Japanese island to unravel whether an underwater structure is the remains of a city lost to the waves or a creation carved by nature itself.

Explorer and marine biologist Monty Halls goes in search of the real stories behind some of the world's greatest underwater mysteries.

Monty Halls and his team are off on a boys own adventure looking for treasure in Namibia, one of the last places that you would imagine for a diving trip. They are heading to Lake Otjikoto, in the north of the country, where they hope to find a safe full of German gold coins, rumoured to have been thrown into the lake in 1915.