New Scientist tells the story of dolphins using tools to hunt:
Simon Allen, a behavioural ecologist at Murdoch University in Perth, Australia, was out on a routine survey when one of the dolphins surfaced “with a monstrous shell oriented skywards”. It shook the shell up and down, and left and right. After a few minutes it disappeared underwater and re-surfaced with five other dolphins encircling it. “This weird encounter we thought might be play or showing-off,” he told New Scientist. But that evening when they developed photos of the encounter, they spotted the dolphin slurping a fish from the shell.
The team speculates the dolphins may chase fish into the conch and then raise it above the surface, knocking the shell around to stun the fish before tipping it into their mouths.