Brisbane commercial lawyer Alexandra Geelan is so afraid of fish, she won't swim in open water.

Key points: Research shows 15 per cent of the population will develop a phobia during their lives

Research shows 15 per cent of the population will develop a phobia during their lives A fear becomes a phobia when it stops people from performing every day functions of life

A fear becomes a phobia when it stops people from performing every day functions of life The stress people feel about their fears is very real and needs to be acknowledged

"I'm as scared of fish as most people are of sharks," Ms Geelan said.

It is an unusual fear, which Ms Geelan, 25, said some people even mock.

"A lot of people just laugh at me — most people don't take me seriously when I tell them I'm afraid of fish," she said.

"When on holiday, I've had people catch a fish and throw it at me as a joke, when they don't realise how serious it is."

Phobias are more common and more serious than you think.

Latest research from the Federal Health Department showed that one in seven Australians, or almost 15 per cent, will develop a phobia or anxiety disorder during their lives.

Phobias often start in childhood but can occur at any age and are roughly twice as common among women than men.

Dr Robert Raven, 66, is a world expert on spiders and the Queensland Museum's senior curator of arachnids.

He has named more than 400 new species and has been bitten by over 100 spiders but has been afraid of spiders since he was a boy.

Dr Raven tackled his fear of spiders by becoming an arachnologist. ( ABC News: James Oaten )

Dr Raven's father was a mining engineer who worked in underground mines in Coober Pedy in outback South Australia.

As a child, Dr Raven was told stories by his father about the proliferation of spiders in old mines.

"He told me about going into a disused mine shaft and lighting flaming newspapers to burn the spiderwebs down as he walked in and spiders would fall down the back of his neck," Dr Raven said.

"It was that mental image of spiders in the dark and just the thought of the spiders on my arm, that I became absurdly fearful of spiders."

Challenging an irrational fear

Dr Raven decided to tackle this fear by becoming an arachnologist.

"I was studying zoology at UQ [University of Queensland] and I needed to adopt a study area, so I thought, 'I have an irrational fear of spiders — alright I'm going to study them'," he said.

"It was my way of challenging that fear … I recognised that the fear was irrational and that I needed to face it."

Dr Raven has named more than 400 new species and has been bitten by over 100 spiders ( Supplied: Dr Robert Raven )

Dr Raven is now one of the world's leading spider scientists.

He has travelled the world, catching and identifying spiders, but admits he has never lost his childhood fear.

"It is still there today — I break out in a cold sweat and I can't concentrate," Dr Raven said.

"I've realised that there are certain situations like when I'm sick that I just can't deal with spiders.

"I manage a shield of calm when I deal with these things — I can physically grab big spiders, but when I'm not prepared, I can't deal with it."

Dr Raven is now one of the world's leading spider scientists. ( ABC News: Shelley Lloyd )

'Full-blown panic attack'

Ms Geelan's reaction to fish is similar.

"I'm terrified of fish … it doesn't matter what size, shape or anything," she said.

"I'm fine with them in aquariums or in little ponds where I can see them, but if I'm in open water and they're anywhere near me, then absolutely not."

Like Dr Raven, her phobia caused a physical reaction.

"It's very similar to a panic attack," Ms Geelan said.

"My heartrate shoots through the roof, shortness of breath, shaking like a real panic attack, and I just have to get out.

"I was walking in the Tallebudgera Creek area [on the Gold Coast] recently and there was a huge school of fish maybe about half-a-metre away and I just started shaking, sweating, heavy breathing and I had to get out of the water as quickly as possible."

Alexandra Geelan deals with her fish phobia by avoidance. ( Supplied: Alexandra Geelan )

Ms Geelan's fear began as a child while swimming on a beach in Perth.

"It started when I was five or six and I was swimming with my Dad and he made a joke that the fish were eating his feet," she said.

"I looked down and all of these fish were swarming his feet and I freaked out and ran out of the water and wouldn't go back in.

"From that moment I've been terrified of fish — pretty much as long as I can remember I've been terrified of fish."

She deals with the phobia by avoidance.

"I don't really swim in open water. I've been on holidays with family to the Great Barrier Reef and my family and friends will go snorkelling and I'll stay on the pontoon or stay on land," Ms Geelan said.

"Most people don't realise how extreme it is — they just think I'll get over it but I actually have a full-blown panic attack."

'Manage the fear through slow exposure'

University of Southern Queensland (USQ) clinical psychologist Associate Professor Gavin Beccaria said the stress that people feel about their fears was very real and needed to be acknowledged.

Dr Beccaria said a fear became a phobia when it stopped people from performing everyday functions of life.

Dr Robert Raven is the Queensland Museum's senior curator of arachnids. ( ABC Brisbane: Jessica Hinchliffe )

"Most of us for example might fear something like snakes, but if you don't want to go bushwalking at all because you're worried a snake will pass you on a track, then maybe that's going into the area of a phobia," Dr Beccaria said.

He said a significant proportion of the population could be living with an anxiety disorder or phobia.

"It might be as high as 20 per cent but a lot of people have phobias that they wouldn't seek treatment for because it's not severe enough," he said.

He said the gold standard treatment for most phobias was cognitive behaviour therapy.

"Part of the treatment is working with the person to be able to manage the fear through slow exposure," Dr Beccaria said.

Considering that most phobia form in childhood, Dr Beccaria advised parents to always recognise their children's fears.

"It's important that parents acknowledge what's going on and have a conversation with the child about facing those fears," Dr Beccaria said.

"Parents need to acknowledge the distress and work with the child to manage the fear."