As our cruiser boat drifts towards the island's shoreline, slick grey heads start popping up from the rocks. The small posse of sea lions has been sunbathing on the shores of Blythe Island – a tiny, uninhabited sea lion sanctuary that's a 90-minute boat ride from South Australia's Eyre Peninsula – but our arrival has them excited. Moments after clocking us the famously social and inquisitive creatures are tossing their chunky bodies into the water and racing out to meet us.
"They don't call them the puppies of the ocean for nothing!" laughs our skipper, Matt Waller, who has been running his aquatic wildlife experience company, Adventure Bay Charters, since 2007. As the heads bob closer and we squish ourselves into thick wetsuits, Waller tells us that most travellers who visit Port Lincoln come seeking a grey-headed creature of a different kind. Port Lincoln is the only place in Australia where you can cage dive with great white sharks in their natural habitat. The activity has become a major Port Lincoln drawcard and a big part of Waller's business. When it comes to interaction, however, Waller says nothing beats the experience we're about to have. "Shark cage diving is all about facing your fears, but swimming with sea lions is like falling in love."
He's said the magic words. I pull on my flippers and snorkel, and waddle to the side of the boat. "Just remember, the more playful you are, the more playful they'll be. And don't chase them, let them come to you or they'll lead you out to sea," says Waller as I plunge into the water.
For a few moments, I can only focus on how frigid water is. I catastrophise that my arms and legs will freeze up and I'll simply sink to the bottom like a stone. The moment the sea lions arrive, however, that's all forgotten. Eight females and pups dart around our group of four, twisting and diving and trying to figure out what we are and whether we'll be good playmates. Remembering Waller's advice I do a forward roll, and one of the sea lions does one, too; I swish my body to the right, and another mimics me. Of the dozens of wildlife experiences I've had around the world – from walking with elephants in Botswana, to spotting wild orangutans in Borneo – this is undoubtedly the most intimate.
As we swim and play, the sea lions take turns laying in the seagrass below, gazing up at us with big, black eyes filled with curiosity. Spending time with these gentle creatures, it's impossible to imagine anyone ever intentionally harming them. Yet Australian sea lions were hunted nearly to extinction in the 19th century. They're now listed as "vulnerable" under Australian law, numbering fewer than 12,000, 85 per cent of which are in South Australia. Currently, their biggest threat is commercial fishing nets, one of which Waller had to haul out of the ocean on our way to Blythe Island today.
An hour has slipped away and we're being called back to the boat for hot showers, tea and cheese toasties. Sensing their new friends are about to leave, the sea lions start swimming away, peering back as if begging us to chase them. It takes all the strength I have not to follow these sirens out to sea.
Nina Karnikowski travelled as a guest of the South Australian Tourism Commission.
Regional Express (REX) flies from Adelaide to Port Lincoln up to eight times daily. See rex.com.au
Adventure Bay Charters run sea lion experiences, shark cage diving, and cruises through Port Lincoln's marina to see Australia's largest commercial fishing fleet. Swimming with sea lions is $205 per adult for a five-hour experience. See adventurebaycharters.com.au
Double rooms at the Port Lincoln hotel start from $155 a night. See portlincolnhotel.com.au