SHARK attacks like the one on Ballina bodyboarder Mathew Lee and world surfing champion Mick Fanning have the potential to shatter illusions of control and even bring on depression and anxiety, Southern Cross University psychology lecturer and researcher Dr Jim Donnelly said.

Dr Donnelly, who has provided treatment for survivors of traumatic events, said events like shark attacks can violate the illusion that it's safe to be in the ocean.

He said in most cases, the chance of a shark attack was very small but when they occur it can have powerful psychological effects on victims and spectators.

"There's something very visceral, something very primal, about fighting for your life against any high level predator," he said.

"It evokes a very very different kind of horror or terror because a person might feel quite helpless in that situation."

Dr Donnelly said in some instances, events like shark attacks could result in depression or anxiety.

"For some people that's what goes on, they are crippled by thinking of all the things that could happen, even if they're all low probability," he said.

"As psychology researchers and clinicians we actually try to understand this seemingly essential illusion of control.

"In order to get out and live in the world we have to hold onto that illusion otherwise we would all be sitting on the sofa in the lounge room not doing anything because if you stop and think about all the things that can happen to you it can be quite disabling.

"People who aren't depressed or highly anxious actually maintain an illusion of control over their environment by doing things each day that argue against helplessness."

Dr Donnelly said with things like shark attacks, surfers may also rationalise it in a way that differentiates their situation and helps them distance themselves.

"They might say, I'm going to surf in places where there are very few shark sightings, I'm going to have people around me, so we have multiple pairs of eyes, or that other attack happened because of a whale carcass near shore," he said.

"We assume that if we behave correctly we'll be safe but that illusion gets shattered sometimes and we may need time and support to get back on track."

The psychologist said if a traumatic event like a shark attack was disrupting someone's sleep, resulting in recurrent nightmares, causing them to worry excessively or re-experience the event during the day, or was interfering with their social life or work, they should consider seeking professional help.