Passengers on board Port's Poseidon catamaran yesterday had the thrill of a lifetime yesterday, with a Dwarf Minke Whale performing belly rolls within metres of snorkellers.

The five metre whale, Poseidon’s first true encounter with the Dwarf Minke Whales this season, voluntarily approached the boat at the Agincourt Ribbon Reefs.

Minke Whales are extremely inquisitive, often approaching boats, divers and snorkelers and interacting for extended periods.  Poseidon holds one of three special permits issued by the Great Barrier Reef Marine Part Authority allowing guests to stay in the water with the whales. The direct human-to-whale interactions are sustainably controlled, with permits issued under strict guidelines.  Once a Minke is sighted, swimmers in groups of ten are sent out along a floating line.

Yesterday's Dwarf Minke did a multitude of passes over an hour. Another Minke, slightly larger than the first, was sighted at Poseidon's second reef site.

Local boat operators report frequent Dwarf Minke encounters from May to July, when about 100 migrate into the area around the Ribbon Reefs. Northern Minkes were the only known species until the 1980s, when the first Great Barrier Reef encounters were reported. According to James Cook University’s Minke Whale Project, the GBR winter visits form the only known predictable aggregation of the species in the world.

The JCU Project works closely with reef tour operators, to limit the impact of human interaction and ensure sustainable management of swim-with-whales tourism.

The Dwarf Minke is thought to be a subspecies of the Northern Hemisphere Minke. Born measuring two metres, Dwarf Minkes are among the smaller of the baleen whales, growing up to eight metres and weighing around 6000 kilograms.

Southern Humpback Whales can also be seen from July to September, thanks to their annual migration to Antarctica overlapping with the Dwarf Minkes.