Port St Johns

The dive begins as a search. You meet the charter boat at the launch site at the Mzimvubu river mouth, below the gorge known as the Gates of St John, and travel out to wherever the shoal is working. Nothing is briefed as a fixed site, so you sit kitted while the crew reads the surface, and the entry happens when a bait ball is found rather than at a planned time. Depending on the charter, you may free dive or scuba dive with the shoal and the predators.

In the water it stays shallow. Bait balls can be 10 to 20 metres in diameter and extend to a depth of 10 metres, and may last up to about ten minutes, so the whole encounter sits in the top of the water column and you circle the shoal rather than drop under it. Thousands of dolphins do most of the rounding up, bronze whalers and dusky sharks cut in from below, and the Cape gannet is the predator most closely tied to sardine presence along this coast. Bryde's whales come through the ball, Cape fur seals follow the shoals as far as Port St Johns, and the occasional penguin turns up on the edge.

Conditions decide how much you see. The run is carried on a cold south-to-north current, broken by bands of cooler coastal water where the flow is reduced or reversed, and the water sits between 15°C and 21°C, warm enough for a 5 mm wetsuit with boots, gloves and hood. Visibility ranges from 2 to 20 metres and some operators will not allow diving unless it exceeds 5 m. This is all mid-water diving over deep water, so the dive ends when the action moves off and the boat comes for you.