“AT seventy feet, the shark home team came onto the field. About twenty four of them with sizes from four feet to about eight feet swimming around us. There’s nowhere to hide! And one of them has eaten the ball!”

This is not a passage from a Boys’ Own-style adventure yarn, but from the memoirs of a Swindon man called Ian Purvis.

His book, The Blue Diver, chronicles the early years of a passion that hasn’t abated since it began more than 50 years ago.

At the time Ian, now 75, was an RAF aircraft engineer serving in Singapore. His job enabled him to travel all over the world, exploring shipwrecks, seabeds and reefs, and cataloguing sealife.

Many of us have the odd tropical shell lying around the house, usually bought from a shop at a holiday destination, but Ian is a passionate collector who gathered most of his specimens with his own hands.

He is married to Dawn and the couple have grown up children and four grandchildren. He last dived in earnest last year, heading down 18 metres for scallops off Portland. He has no plans to stop.

The attraction?

“I would have to say it’s not knowing what you’re going to find. It’s this little thing in the back of your head, that today is the day you’re going to see something pretty special.

“It could be a bronze cannon, it could be a shipwreck nobody’s seen before, it could be a big shark or a big crab or a big lobster – or a bagful of scallops that you’re picking up to bring home for supper.

“That’s the thing about diving – you swim along the bottom and you’re looking, always looking.”

His encounter with the sharks – one of many over the years – came during an underwater scientific expedition in 1972 and 1973 to the Egmont Islands in the Indian Ocean.

The science was under the control of Dr David Bellamy, who was already well on his way to becoming one of Britain’s most famous naturalists. A few years later, Ian was a guest during Dr Bellamy’s appearance on This is Your Life.

A chapter of The Blue Diver is devoted to the islands. Ian identified dozens of species of mollusc, and his data and specimens were sent to the Natural History Museum. There was plenty of other wildlife: “...I looked up towards the surface and saw two great manta rays swim over us. What a sight. I had never seen mantas before. It was fantastic. They were probably 15 foot wingtip to wingtip and were performing an underwater ballet... They rolled over each other, swam belly to belly towards the surface and then peeled off together in perfect unison.

“No aircraft display team could have completed such perfect manoeuvres. It was a joy to watch.”

The creatures gathered by Ian for study during the expedition included coneshells – carnivorous sea snails with a venomous sting – and he became very ill after one jabbed him as he examined it later onshore. If the snail had been bigger he might have died.

There have also been touch and go moments underwater. One came while he worked 120 feet beneath a drilling rig in the Middle East, and an assistant on the surface inadvertently cut off his air for a while. Ian said: “He didn’t understand all the English words I used, but he got the gist of it...”

The other, while repairing machinery beneath a reservoir at Birdlip, was the stuff of nightmares. Ian had sealed off the water in order to pump out the machinery, and was working without gear in mud and slime at the bottom of four ladders.

“I was measuring up this pipe and I could hear this whistling like a tube train coming along a tunnel.”

The seal had moved and the chamber was about to be flooded. A rope attaching him to the surface snagged on a ladder, and Ian only escaped after persuading a colleague on the surface to let go of the line altogether – which then became coiled around him.

“The thing you can’t do is panic underwater. Once you panic, your thinking system fails. When you read things about divers who’ve died, it’s because they’ve panicked.”

The book ends in 1976, when Ian left the RAF due to a back injury. He plans a further volume, which will cover his later career in commercial diving.

  • The Blue Diver, ISBN 978-0-9929322-0-6, costs £7.99. It is available from Pen and Paper in Victoria Road, and from Ian himself, who can be reached at ian.purvis910@gmail.com