It seemed like a fair swap – Nigel Rennie taught the Rev Andy Norris how to sail after Andy had taught him about Christianity.

Nigel helped his local vicar through his sailing exams to thank Andy for leading a 10-week Alpha course that explained the basics of faith.

The 53-year-old sailing instructor and examiner was part of Andy's congregation at St Mary's Church, Warsash, before Andy, now 51, moved to become rector of St Mary's Church, Alverstoke, this summer.

And Nigel was one of 3.3 million people in the UK and 22.5 million people worldwide to experience Alpha. Participants meet one evening a week for a shared meal, to hear a talk about an aspect of Christianity and then to discuss those issues in small groups.

The philosophy is that no question asked is out of bounds, and participants can ultimately decide whether Christianity is for them. Alpha and other basic Christianity courses have helped millions to understand more about faith and become more involved in their local churches. Alpha is the most well-known of these courses. Other courses such as Christianity Explored or the Emmaus Discipleship Course also unpack the Christian message.

Andy and Nigel actually became friends when Nigel's son Thomas became seriously ill when he was just six weeks old. Thomas had a heart condition and was taken into St Mary's Hospital in Portsmouth, where his heart stopped twice. Andy was Nigel's vicar and visited the family in hospital. Nigel and his family had recently started coming to St Mary's Church in Warsash.

"I remember the first time Andy tried to visit, he didn't actually get there because his car caught fire on the M27," said Nigel. "But he did get there, and it is out of that kind of adversity that friendships are often formed.

"I've been part of the military – in the Royal Electrical and Mechanical Engineers – and had been spiritual, but not religious. I'd visited war zones and had skippered army yachts, and I'd always found the padres to be good people to speak to.

"There were three incidents that made me think more about the preciousness of life. One was when I had to steer a boat into Crete in a Force 10 gale. Afterwards I sat in a church for a while, realising that I was mortal.

"The second was in 1997 when I was in a yacht in the Pacific. There was a Force 12 storm, the boat rolled over and was ultimately lost. We were in the water for two hours and the people sent to rescue us lost their lives.

"And the third was when Thomas was ill in 2005. The problem was eventually traced back to a nerve being trapped in his neck, and he is now in perfect health.

"Although I was coming to church, it became more of a priority after Thomas was ill. I wanted to be a full member and to be confirmed. The Alpha course was in Andy's home and 12 of us sat around the dining table for a meal, and then in his front room to watch a DVD and talk. The whole ambience was good – it was adding to what we knew and it was fun.

"I was confirmed by the bishop in the cathedral in February 2012, and Alpha definitely made me feel happier in the church environment.

"The videos were brilliant and I'd say to anyone thinking about it that they should do it. My kids loved Andy's services and the Messy Church at St Mary's, and we're pleased to be part of the church."

Meanwhile, Nigel had been helping Andy learn how to sail. They had sailed back from Cork in 2007, with Andy skippering for the first time from Falmouth back home. Then in 2012 Nigel helped Andy to prepare to sail around Britain, and mentored him for his sea survival and diesel engine courses. And he helped him through his yachtsmaster offshore exam earlier this year. Nigel is an instructor/examiner for the Royal Yachting Association, so knew what would be required.

"Nigel was determined to get me through the exam before I left the parish," said Andy. "It was his parting gift to me, because if I'd done it commercially it would have been quite expensive."

And Nigel said: "I do think each of us should use our skills to help each other. You can't always help the person who helps you, but I was more than happy to help Andy through his exam as he had been such a support to me and my family."

A similar course to Alpha is Christianity Explored, which is run at St James' Church in Emsworth. It also involves a meal, a talk and discussion groups.

When Barbara Crick moved back to Emsworth, she started going back to St James Church, where she'd been as a child. She thought its Christianity Explored course would be a good way to get to know people.

In fact, it's resulted in a deepening of her faith and prompted her to go to church more regularly with her sons Josh, 5, and Sam, 3. She's now part of a house group that studies the Bible and prays together.

"We moved back here two years ago after living and working in Cambridgeshire," said Barbara, now 33. "My husband Shaun had his own business, Hollybank Builders, and I started my own business, Emsworth Cookery School. So we could move to be closer to my parents.

"I went to St James Church occasionally and so did my mum. I'd always enjoyed church when I went as a child. I'd heard of Alpha, but not Christianity Explored, but it sounded like a good way to get to know people. So my mum and I went together.

"I was in a discussion group with others who were my age, and we all got on well. We could discuss anything. I remember being at a toddler group with Sam and hearing the story of Noah. I thought it sounded like God being quite mean, so I asked about that in my small group.

"I got answers to my questions, but it was interesting to hear people with different points of view in our small group. I think we recognised that there wasn't always a straightforward answer.

"I did the course a year ago, and I've joined a home group since then, which happens to include plenty of mums and meets during the day. We can talk about issues like parenting and understand more about faith. I definitely don't feel as peripheral in the church, and I do make more effort to be there on Sundays.

"I'd say to anyone who was thinking about Christianity Explored that they should go for it. It's open to anyone and is a platform to ask questions. But if at the end you're not convinced, that's fine."

The next Christianity Explored course happens on 10 Tuesday evenings from September 17 until November 26, in the Pastoral Centre, in the Square, Emsworth. It starts at 7.30pm and includes a meal, the chance to watch a DVD and to join in discussion. Details on 01243-373465 or 01243-372428.

St John's Church, Locks Heath, is running a taster session for those interested in a Christianity Explored course. You can ask questions and get a flavour of the course at 11am on Sunday 29 September. Contact Kath Sugden on 01489-578082 for details.

An Alpha course run by St Mary's Church, Portchester, will start at Highclopes Community Centre on Carlton Road, Portchester, from 7pm on Thursday 19 September and continue each Thursday night. Contact the Rev Ian Meredith on 023-9237 5422 for details.

St James Church in Clanfield is running an Alpha course for 10 to 15-year-olds from 6.30pm-7.15pm, starting on Tuesday 24 September. The adult course starts at 7.45pm the same night. For details, contact the Rev Anne Gothard on 023-9259 6315.

And St Jude's Church, Kent Road, Southsea, is launching its Alpha course at 8.45pm on Friday 4 October, which will continue on Fridays. For details, ring 023-9275 0442.

Source: Diocese of Portsmouth