The boat glides through the tranquil waters of the Hawkesbury River near the village of Mooney Mooney, about 45 minutes north of Sydney, where only a small sign on a pier reveals that there is an oyster farm beneath the surface. The farm belongs to Sheridan Beaumont and her family, who offer tours for visitors here. “Who wants to hold some baby oysters?” Beaumont asks, pulling two long containers out of the water containing several small oysters. The visitors, all wearing waterproof fishing overalls with sewn-on wellies, cautiously take a bite. Beaumont explains that the sea creatures are rais…