What's it like to witness the great tide?

Catching a glimpse of the great tide along the eastern coast of South Africa is like watching a raucous bar fight. It starts with a pod of dolphins bullying a pack of sardines, and before you know it, it's a swirling mass of sharks, whales, seabirds and seals. Yet, the scuffle of great tide exhibits a dazzling choreography in the way that it unfolds. Tens of thousands of sardines swim in dizzying synchronicity for protection. Around them, dolphins dance and twirl nimbly, attempting to chase down the wily prey. Snow white Cape Gannets dive headfirst into the water like avian torpedoes.

Why such a frenzy? Cool waters from Antarctica have drifted northward into the Indian Ocean, and the migration of 500 million sardines up the coast of South Africa has commenced. For a host of predators that track this annual phenomenon, it's also time to tuck in for a hearty winter meal.

Sardines thrive best in cooler waters no higher than 70 degrees Fahrenheit (21 degrees Celsius). In the Southern Hemisphere, winter occurs during June and July, and sardines follow the colder Antarctic along the shallower waters of the eastern coastline of South Africa. Packed together tightly, the enormous shoals of sardines may stretch for 15 miles (24 kilometers), like a massive trial of ink in the ocean. Predators loom in the distance, awaiting the hoards of prey.

In the summertime, sardines are more dispersed and reside in deeper waters farther from the coast. Dolphins, which are particularly adept at rooting out sardine shoals, rouse their prey toward the ocean surface, corralling groups into bait balls that are easier to devour. Golden-crowned Cape Gannets follow the dolphins and plunge from 100 feet (30 meters) in the air into the water as fast as speeding cars. Streams of tiny bubbles mark the Gannets' underwater paths like smoke from a jet engine. Sardines shift and dart in unison to distract the invaders.

When the Great tide begins and millions of sardines head northward, superpods of 5,000 dolphins and countless Gannets litter the ocean. The predators linger near the Waterfall Bluff, a coastal inlet that disrupts the sardine migratory path and can entrap them. When this happens, dolphins and Gannets are the first on the scene, but sharks, Cape fur seals and Byrd's whales arrive soon after. Cape fur seals take advantage of the sardines' proximity to the coastline, and the sharks assault the pre-formed bait balls. The 50-foot (15-meter) whales can gulp 10,000 sardines at once.

Described as one of the greatest predatory gatherings on Earth, the climactic combat of the annual sardine run is at once savage and breathtaking. Fins, feathers and flippers flail against the ocean current to snag a precious snack. But somehow, the competitors avoid harming each other by maneuvering elegantly amid the fracas. And when the shoal has been feasted upon and the lucky surviving sardines escape, the waters calm. The spring sun warms the Indian Ocean and sends the sardines and their predators back to the Cape of South Africa to begin anew until the next great tide.