It was suddenly just there. I had been staring down through my face mask into the silky, warm waters of Ningaloo Reef - sunlit surface above, gently inky depths below, Ellece Nicholls beneath me, like a mermaid, pointing - seeing nothing but the swishing, coral-spawn speckled sea, when there it was.
The whale shark appeared out of the blue, quite close, spotted, sharp-tailed, oval mouth vacuuming plankton. The oceans' biggest fish, Rhincodon typus, with the biggest recorded at 12.65m. A slow-moving filter feeder. A threatened species and still mysterious. What are their other most important feeding grounds, where do they breed, where do they give birth?
I have long wanted to see this (it was my New Year's resolution to swim with a whale shark) and here I am and here it is.
Most of us have seen the big, blue photographs and the "swim with a whale shark" slogans in what has become one of the iconic symbols of the West Australian environment, wildness and eco tourism. Here one is, in the flesh before me, gills pumping, eye clearly visible, a small flotilla of hanger-on fish under its soft, white belly, and it's personal.
I hadn't expected that. For just this moment, it feels just like it's me, alone with this elusive and mysterious shark. Me with nature - a human feeling simply part of that nature.
I didn't say this to Ellece, who is in her second full season with whale sharks, but I know it will delight her when she reads this.
For this 22-year old, who grew up in Baldivis, started on a dolphin swim boat in Rockingham aged 16 and has tackled a double degree in commerce and science at Curtin University, says: "I want everyone to have their own little experience - just to feel they are on their own with the shark."
And I do, despite the other 17 people on the Three Islands Whale Shark Dive's boat Draw Card, split into two swim groups to conform with the strict code of practice the industry and environmental science experts have devised for Western Australia. At this moment, I do.
The day had begun at 7.20am in Exmouth when we were picked up from our accommodation and driven by coach half an hour to the boat, then ferried out to Draw Card by inflatable dinghy.
There are five crew on board, and a spotter plane up in the air, looking for whale sharks. Mentally I divide the $375 by the nine hours I will be out with Three Islands Whale Shark Dive, and then factor in the five people, the plane, boat, dinghy, coach and meal costs.
For that alone it is good value; for the experience itself, it is priceless.
Once on board the boat, we are briefed on the rules of swimming near whale sharks - certainly not in front, certainly not within 3m either side of the body.
Then there is a morning swim just to get the confidence up and for the crew to see everyone snorkelling. It is followed by a comprehensive morning tea.
But it isn't long after that that the boat veers.
"We are about 10 minutes from a whale shark. Everyone get yourself ready." Having been supplied with masks, snorkels and fins, we get them ready, group one first near the marlin board.
Then we are in the water, following instructions, leaving a clear passage for the whale shark. And there it is, appearing out of the blue.
This first whale shark is about 4m long, a fine male. (It is one of Ningaloo's mysteries that the whale sharks feeding annually here after coral spawning are male.)
One group is in the water, then the next, then the first group again - thus restricting the number of swimmers near the whale shark. It is run very professionally and I notice Ellece helping a less gung-ho snorkeler gain confidence.
She swims ahead, pointing to the shark, keeping swimmers in the correct position.
The boat steams off to another sighting, and there we are treated to a 7.5m whale shark. It looks like a submarine. It swims slowly and we track alongside it, comfortably keeping pace.
When my group gets back on board, the whale shark follows us, right up to the duckboard - clearly unaware of the 3m rule. "It's quite unusual," says Brad Norman, with understatement. Mr Norman is the world authority on whale sharks (see story below).
The final whale shark of the day is 4.5m.
Three whale sharks - one of which dives and comes back up and we swim with it again - four big swim sessions. I have lost count of how many times we were in the water.
Only after all of this are we treated to a big cold lunch before heading back to the boat ramp and taken back to our accommodation at 4.30pm.
It is early in the season, and the crew is clearly rapt. The whale sharks will be cruising through here probably until the end of July. Last year was the record. So far.
The last word must go to Ellece. "Wasn't he just beautiful? Did you see the markings behind his gill and that big tail …?" She jabbers on and on excitedly, eyes wide. You'd think it was the first time she'd seen a whale shark, she's so thrilled and pumped. It isn't. But you'd think it was.
And I can understand that.
• Three Islands Whale Shark Dive's whale shark season is from March to July. The full day is $375 for adults, $265 for children, $275 as an observer, and there is a package price of $1130 for a family of two adults and two children under 16. It includes the coach transfer, boat with five staff, tender, snorkel gear, morning tea, lunch and afternoon snack. The business, established in 1997, is an accredited tourism business and eco-certified by Ecotourism.
See www.whalesharkdive.com and call 1800 138 501 or 9949 1994.
• For more on Brad Norman's work, and the Ecocean research project, see www.whaleshark.org. Ecocean has an event at Royal Perth Yacht Club on May 21 to raise funds for data-logging tags for whale sharks.
• For more on Ningaloo Reef and Exmouth region, see www.australiascoralcoast.com.