Electricity and water might seem an unlikely combination, but Colm Spain, an electrical contractor, has a passion for diving. "Maybe it's the two extremes," he laughs. "They say one way to forget about your job is to go diving, and a bad day's diving is still better than a good day at work."

Like many Irish divers, Spain, who is from Dublin, came across the sport abroad. He was pleased, and not a little surprised, to find he could easily continue his hobby in Ireland after two years in Australia.

The coast is now dotted with thriving diving centres, and enthusiasts report that Swedes and Norwegians, in particular, are exploring our waters.

These days, Spain makes for Cork and Kerry rather than Wolf Rock or Comboyuro Point when he fancies a spot of diving. But surely what this country has to offer suffers by comparison? Not so, says Spain, who insists Ireland has its distinctive charms.

"Here, you'd be coming out of the water shivering, but it's lovely, in a way. There might be a huge open fire on the beach. You run up and have a mug of soup and you're just delighted with yourself. There's a sense of achievement," he says.

Respecting the "buddy system" is as essential here as elsewhere if you want to be a successful and safe diver, he says. That means you have the benefit of your diving partner's equipment and experience to back you up should anything go wrong. But inadvertently losing contact with your buddy underwater can be very frightening.

Spain tells the story of a dive when visibility was so poor that he lost contact with his buddy 35 metres down. "I looked around for him for a few minutes. Then my torch went out completely. I only knew which way was up by the bubbles."

It can be easy to become disorientated in such a situation and discipline is essential, he says.

"In a hairy situation, you just want to get out of there, but of course you have to control your ascent rate and go up slowly. It's so quiet and eerie. The only sound is yourself breathing, and every breath you take is so loud."

As it transpired, Spain's buddy was doing exactly the same thing, and the pair popped up on the surface at the same time, but the experience taught him a lesson.

"You should always stay close to your buddy. At the end of the day, he's your lifeline and you're his. You just can't go off and do your own thing."

The bond of trust that builds up between diving partners is unbeatable, he says. "After the first or second dive, it feels like you've known them for years. There's a sense of trust in the other person."

Spain quickly built up that kind of trust with a German girl who he was diving with for the first time, when his essential weight belt started to come loose. "I was trying to buckle it, but you have gloves on and everything. You can't even look down properly because you have so much stuff on. So the German girl I was diving with said: 'Listen, let me try.' In the end, she had to sit on me to try to keep me down. When I came up to the surface I got a terrible slagging."

But diving isn't a dangerous sport, insists Alfie McCaffrey of the National Diving School, in Malahide, Co Dublin.

Naturally, there are hazards and risk factors, he says, but injuries are almost always caused by divers themselves. He rattles off figures that show diving is safer than cycling, horse-riding - even tenpin bowling. You don't have to be superfit to dive, but you must have your wits about you at all times, he says. "It's about using your brain, not your brawn. You're in the sea, and it's a capricious mistress at the best of times. You must treat it as you'd treat any lady: with the greatest of respect."

McCaffrey says the rules and guidelines exist for divers' safety, and if they're followed to the letter, it's a safe and exciting sport. "I can take out top-class insurance cover, for £60 a year, that allows me to dive anywhere in the world."

McCaffrey says aspiring divers are never pushed beyond their capabilities. Training takes place in a swimming pool before novices try out their new skills in the sea. "If you need more time, you get it. No two people are the same."

He has seen all sorts of people take up the sport in recent years, a trend he puts down to better education, more disposable income and, especially, more travelling. "People are going abroad and seeing what's available. They're getting into dives in Australia, Thailand, the Red Sea - and coming back, looking for more."

He says that diving is an excellent activity for cardiovascular fitness, and that there's a cracking social life to go with it.

PADI, the US-based dive-training organisation with branches all over the world, recently signed its 10-millionth diver, testifying to the increasing popularity of the sport.

McCaffrey says diving has attracted information-technology professionals, managers and the self-employed in recent years. "It's not to do with income," he says. "It's to do with the person's outlook on life. That's a big deciding factor."

What unites them is a sense of adventure and a continuous desire for a new challenge, he says. "We all need to strive for something outside of our normal, everyday lives"

Taking up diving shouldn't work out as too expensive a hobby if you do it properly, he says. In particular, there is no obligation to buy any equipment immediately. "They can continue to rent until they're sure they're comfortable in the water."

One of the most exciting aspects of diving around the coast of Ireland, particularly in Co Antrim, is the opportunity to look at a wreck at close quarters. "It's always remarkable and mysterious when you think about how it got there. You can let your mind wander in all sorts of ways. There's always a certain amount of romance and mystery about wrecks."

Michael Loftus, of the D·n Laoghaire-based Irish Underwater Council, puts diving's increasing popularity down to the fact that we live on an island. "People have always had an interest in water, and it's natural to want to explore."

Loftus says an introductory course should cost between £150 and £200 and include membership of the club for a year. He estimates that basic equipment for pool sessions - fins, mask and snorkel - will cost between £50 and £60. Afterwards, a semi-drysuit will cost around £200, with the price rising to £300 for a drysuit. "We have a guide price if you want to be fully kitted out. When you tot everything up, you wouldn't be far off £1,000."

Some second-hand equipment is acceptable, but certain items, such as breathing apparatus, should be new. "That's something you depend on for your life, so you wouldn't want to take the chance of ending up with something that wasn't working properly."

Loftus says his organisation is affiliated to CMAS, the federation of dive-training organisations, which means divers who gain their qualifications here can dive anywhere in the world. "It's like a worldwide driving licence for divers."