I've not often been spooked by marine animals but I must admit to a few occasions when that happened. One was on a dive trip to Myrmidon Reef.
Myrmidon is one of the most spectacular dive spots on the Great Barrier Reef. It is perched on the edge of the continental shelf where the up-welling, nutrient-rich waters support an amazing variety of marine life.
The water is crystal clear. Sometimes you can see well over a hundred metres. If that doesn't impress you, jump in at one end of a fifty-metre swimming pool and take a look at the other end.
One day we arrived at Myrmidon and anchored in the lagoon. The tide was about to turn and we separated into groups for our first dive. I took my group to a spot where you can peer down into the depths far below. I chose a slender coral pinnacle as an observation platform. I'd been there before and the view is stunning.
On this occasion, it was particularly impressive. The coral pinnacle was alive with brightly coloured reef fish and pelagic fish could be seen swimming lower down.
A small shark caught our attention. It was surrounded by a shoal of tiny fish and was heading towards the surface. They rose together and got bigger and bigger ... it was amazing how big they got!
When diving, there is a tendency to judge distance by clarity. Things that look clear are assumed to be near. In the ultra-clear water of the outer reef, we had hugely underestimated distance.
The shark wasn't small. It was gigantic and the fish accompanying it were far from tiny. As they got neared, we recognised the shark as a bronze whaler. The fish were barracoutas. The shark took no interest in us but the barracoutas began to circle the pinnacle on which we were perched ... and that was a bit scary.
The barracouta is a Halloween fish: the sort you dream about in nightmares. Its head is a third the size of its body and vicious teeth protrude from its gaping jaws. Our barras were about half-a-metre (20-inches) in length and there were hundreds of them.
I'd dived with barras before and wasn't particularly put out by their presence. The same couldn't be said for some of my companions. One or two looked on the verge of panicking and, as divemaster, I had to calm things down. I gave the signal to ascend and, when we reached the surface I signalled to the dive boat for a dinghy to come and pick us up.
No one signalled back. There was some sort of disturbance. The crew evidently had a problem and I'd have to cope without them. The sensible thing was to make our way back to the boat on the surface. I figured that the barras were fascinated by the coral pinnacle and not by us. We'd soon get clear of them.
But we didn't. The fish came with us. We tried swimming under the water but it made no difference. They kept coming, beady eyes staring, mouths gaping, always circling.
By now I was starting to get a tiny bit apprehensive. I'd never heard of barras attacking divers but there could always be a first time. It they did, the wounds would be horrific.
I told myself there was nothing I could do about it and my first duty was towards my charges. The risk from the fish was minimal. The risk from panic was far more serious and, from the look on some people's faces, that seemed on the cards.
We kept going and the dive boat came in sight. I saw it through a swarm of fish. They were mainly barras but there were other pelagics amongst them, including the bronze whaler. For some reason the fish had been drawn towards the boat and were congregating around it.
Divers were in the water trying to get on board. I guessed we were not the only ones to be spooked by the fish. There were barras everywhere and some were huge. I'd never seen any so big before ... at least a metre-and-a-half from tail to snout ... and they were making aggressive plunges at people.
Suddenly it was all over. A crewmember jumped into the water with a speargun and shot one of the big barras, which took off like a rocket. Seconds later there was hardly a fish in sight. The bronze whaler was gone and so were the barras. The only fish that remained were the tiny reef fish that lived amongst the corals.
When we came to look at the spear, which had been fired at the barracouta, we found that the end had sheared off. The pronged tip had lodged in the big fish's skull and its violent movements had snapped the metal at the joint.
In all my many years of diving, this is one of the very few incidents in which I saw a speargun used effectively in defence. I remain of the view that fish pose very little threat to divers. I was never happy about the use of spears fitted with the explosive device known as a powerhead. I've seen them used and they are deadly ... not the sort of thing you'd want to see in the hands of an inexperienced operator.