For those aboard a recent whale watching cruise off Cape Cod, the decomposing carcass of a year-old humpback calf floating in the waters of the Stellwagen Bank national marine sanctuary made for a heartbreaking sight. But it turned into a camera-ready moment, and a rare bonanza for shark researchers, when two large great whites showed up and started feasting on the remains. A short video clip captured by the crew of Captain John Boats and posted to Facebook shows the apex predators, one estimated to be at least 18ft, devouring what one whale expert, Peter Corkeron of the New England Aquarium, called “the biggest smorgasbord a shark could ever dream of”. “People on board were pretty excited,” boat captain John Goggin told the Boston Herald. “There was a lot of yelling: ‘Oh my God! Wow!’” Over the next two days, eight great whites showed up along with blue sharks and numerous species of seabird, according to researchers funded by the National Oceanic and Atmospheric Administration (Noaa). In partnership with the Massachusetts division of marine fisheries, researchers were able to tag five great whites. Six of those which turned up to feed were already known to the researchers. The two making their first appearances were adult females, the experts said. The Noaa-funded group posted to Facebook its own extraordinary two-minute video of the mid-August encounter, showing a packed tourist boat in the background. The carcass, they said, would provide nourishment to marine creatures for months. The researchers’ good fortune extended to the whale scientists of the Center for Coastal Studies, a non-profit from Provincetown, Massachusetts, which identified the humpback as an unnamed 2020-born male calf of an adult whale called Venom. “This is an individual who was well known to CCS scientists, as well as whale watchers off the coast of Massachusetts,” the group said in a Facebook update. “The cause of his death is not known at this time. While it is sad to learn that an individual has died, documenting these events is essential for long-term population studies. These efforts are also critical to understand the ongoing humpback whale unusual mortality event along the Atlantic coast.” The statement ended with a warning: “Remember to keep your distance from whale carcasses, whether at sea or on land. Conditions can be more dangerous than they appear, especially if predators are in the area.”