Senior divers left the gloom of British waters behind to chase turtles and exotic fish – and pick up skills they can pass on to colleagues by visiting the warmer waters off Central America.

A team of instructors from the Defence Diving School at Horsea Island in Portsmouth headed off to Belize for a two-week expedition to hone their skills in waters not clouded by the mud, sand and rubbish which creates poor visibility for divers at home.

The team picked the waters around the Blue Hole – a famous deep-diving spot off Belize – for the expedition.

Lt Allan Youp, head of diving training support at the Defence Diving School, was part of the RN contingent and said the experience was a world away from the joys of Horsea Lake.

“Belize is blessed with the second largest reef in the world, which provides numerous gullies, drop-offs, walls and the occasional swim through,” he said.

“Gullies in the reefs were home to morays, lobster and the occasional crab the size of a tank.”

The RN officer picked up the nickname ‘Nitro’ after suffering the effects of nitrogen narcosis during one deep dive, but luckily Royal Engineer Capt Chris Jarvill was on hand to help out.

And first aid expertise was also put to practical use when a young boy snorkelling near the expedition suffered a shallow-water blackout.

The Service divers pulled the youngster on board their boat and gave him oxygen until he showed signs of improvement, using training they had received back in the UK.