South African civil society has halted a planned intensive offshore seismic survey of the country’s south-eastern coastline by oil giant Shell.

Activists had claimed unsuccessfully in a separate court action that the process of firing sonic waves into the ocean floor to map it for potential oil and gas reserves would cause "irreparable harm".

On Tuesday last week, a High Court ruled in favour of an interdict to stop the Shell survey amid a growing consumer boycott of petrol stations selling Shell petroleum products.

The second court ruling against the survey came largely as a result of evidence from a wide selection of leading oceanographers showing that the seismic exploration along South Africa's famed Wild Coast would "result in permanent harm to the ecology of the surveyed coastline".

The survey had the potential of finding significant reserves of both oil and natural gas while ecologists and oceanographers feared it would harm dolphins, whales and many other marine creatures, endangering the entire coastal eco-system.

The court ordered an immediate halt, with the oil giant and the South African minerals minister ordered to pay costs.

The second attempt by civil society groups to stop the survey was successful in part because of convincing scientific arguments and because environmental impact assessments and local community consultations either had not been done or were grossly inadequate.

This means that Shell's permit from the Ministry of Mineral Resources and Energy may also stand to be legally challenged.

The implications for South Africa run deep.

On the one hand, a major gas and oil find in relatively shallow waters on the continental shelf would be a huge boost for this country's ailing economy.

On the other hand, there is the likely negative impact on marine life and ecology, especifically humpback whales which migrate along this coast, most likely to be hurt, killed or disoriented by the sonic "assault" they would endure in a key habitat.