Guided oyster safaris are one of the signature experiences of the Bohuslan coast, and Grebbestad is one of the best places to do them. You wade out with a guide at low tide to harvest flat oysters from the rocky inlets, shuck them on the spot, and eat them with a squeeze of lemon and a glass of Muscadet or locally brewed beer.
The experience is simple and genuinely pleasurable. The water is cold and clear, the granite rocks are slippery in interesting ways, and eating an oyster you've just pulled from the sea yourself is a different thing from eating one on a restaurant plate. Several operators run safaris from the harbour in summer; book ahead, as they sell out.