SIYABONGA SISHI  SOUTH Africans took to their beaches on Sunday to protest against plans by Royal Dutch Shell to do seismic oil exploration they say will threaten marine wildlife such as whales, dolphins, seals and penguins on a pristine coastal stretch. A South African court on Friday struck down an application brought by environmentalists to stop the oil major exploring in the eastern seaboard's Wild Coast, rejecting as unproven their argument that it would cause "irreparable harm" to the marine environment, especially migrating humpback whales. The Wild Coast is home to some of the country's most undisturbed wildlife refuges, and…