IT was a watery bang and a blinding flash that started it.
Standing on a surfboard I collided with another. His shin met my face and it was not a friendly greeting.
I got myself to shore, assuring him and my surfing friends nearby that I was fine. Except I wasn't. I lowered my board safely to the sand, but suddenly I could no longer stand up. Just above the waveline, I was suddenly quivering and retching.
Two friends who are nurses took command and I found myself lying prone, in the recovery position.
Such helplessness is neither familiar nor comfortable for one as independent as I am.
As I resurfaced from the mental fog, a passing GP stopped and assessed me, saying I was clearly concussed and should see a doctor if I was not right within a day or two.
I wasn't: my head hurt, my reactions were a little slow and I felt dopey. My teeth ached and my eye was bruised.
The GP said all symptoms were consistent with concussion and he ordered a CT scan to rule out a slow cranial bleed. He said concussion is taken far too lightly, and I agree.
Brains are imperative to our every action and thought, our feeling and our doing. And yet, if we are sporty, we would not expect to escape childhood without at least one good head pounding.
We rally to watch big boxing events like last weekend, where the objective is to punch an opponent senseless. A primal urge is pricked. We bay for blood and brutality, urging the bloke in our corner to beat the living daylights out of the other guy, to beat his head until he can't stand anymore.
On the football fields, we weigh up how severe the head knock was before deciding if a player should come off, lauding those who play on. It happens every week in almost every top-level game.
And yet science shows damage from concussion is like a creeping damp, with the sum of little whacks being more potentially damaging than one bigger one.
I have had more than half a dozen concussions, with two leading to hospital admissions in childhood. The combination of being active and accident-prone bred familiarity with emergency departments.
Brains are so vital, so well-built and yet so easily hurt.
My CT scan ruled out a brain bleed, but turned up something else: a 7mm protrusion into a space where brain matter should not deign to go. I was sent on to a brain specialist and put on an emotional rollercoaster.
In the daylight, I felt positive and anchored. At night, I worried I was heading for an early death.
I have seen what a fortress the head can be. I held the hand of someone dear as they endured the punishing regimen that is radiation treatment and chemotherapy for brain cancer.
I saw how the brain is built to protect itself, so that once an invader is within, bombardment from without via radiation has limited success, and the brain/blood barrier deflects the powerful chemo drugs.
I had seen what it is to die despite the best that science and nature has to offer.
The referral to the neurosurgeon was followed quickly by an MRI. I held my breath.
Thankfully, blessedly, the abnormality was deemed to be manageable.
I have nether a malignancy nor an infection. My brain may not be like most others, but I am mostly uncompromised and the condition is not going to immediately truncate my life.
It can cause headaches, slight disorientation and marginally slower reaction time, but I can live well with those.
I am lucky. And now I feel the vigour that comes with being lifted by life's second wind.
Brains are so vital to our every function. We need to take care of them, protecting where possible against damage and nursing them gingerly when a bruising occurs.
We need to rethink the adoration of boxing and brute force on the football fields.
It does not take much thinking to realise that.
Dr Jane Fynes-Clinton is a journalism lecturer at the University of the Sunshine Coast.