Shark-cage diving in Gansbaai and cold water plunging: what they’re really like

“Scared?” the guide asks with a sympathetic smile. It’s a mid-winter morning and I have brought an American friend to Gansbaai to tick something off his bucket list. Marine Dynamics’ shark-cage diving expeditions begin at its HQ with breakfast and a briefing, where the swimmers are sized up for wetsuits. I say I won’t need one as I’ll be watching from the boat. The guide isn’t wrong. I am scared – but not of the sharks. Winter on land in the wet, windy Cape is not for sissies. Swimming in the icy Atlantic? A hard no – even with a wetsuit. “We’ll pack you one in case,” he says.

The briefing is mainly about safety (keep your fingers inside the cage) and what we might see. For years, Gansbaai was marketed as “the great white shark capital of the world”. But sightings started dropping around 2015 and are today rare. At the time of writing, the last recorded one was in October 2025. A favoured explanation for this is a pair of male orcas, Port and Starboard, who began systematically hunting great whites here around 2017. Keen to keep their apex predator status, the simplified story goes, the rest moved on.

But Marine Dynamics – whose shark-diving and whale-watching trips double as data-collection runs for its research and conservation efforts – says humans played a part too. Lethal shark-control measures in KwaZulu-Natal, along with fishermen depleting the whites’ prey along the coast, meant numbers were already down by the time Port and Starboard arrived. Those serial killers with the nautical nicknames were effectively the last straw.

A consolation for the shark spotters, though, is that another species has skulked in to fill the gap. Bronze whalers, or bronzies, were once rarely spotted here. They are, in fact, a prey species of the great whites, but as the whites dwindled, bronzies began to boom. No promises, of course, says guide Susy Alexandersen as we walk to the harbour, but they’re now the sharks we’re most likely to see.

A 20-minute ride on the double-decker catamaran Slashfin takes us to the dive spot near Dyer Island. About 8km off the coast, Dyer is a CapeNature reserve whose surrounding waters are prime “marine big five” territory: whales, seals, penguins, dolphins and sharks.

With the anchor dropped, the crew set to work “summoning” the sharks. The strategy is chucking in chum – a slurry of fish oils and bits of flesh – whose scent should pull in any passing predators. Gannets circle overhead, mullets crowd around the boat and it isn’t long before the first shark appears, a flickering shadow beneath the surface, fractured by sunlight on sea. The first group of divers drops into the cage, clamped to the side of the boat.

Alexandersen on the mic, meanwhile, is dishing up facts. Though they share a common prehistoric ancestor, bronzies are different from great whites in several ways. Maybe most importantly, they are highly social, often seen in large groups. This is soon borne out around the boat as one becomes two. Then three. Eventually it’s eight, Susy counts – plus one nosy stingray.

The divers, meanwhile, are going under.