next to the site where MV Smart sank, I have spotted a row of underwater sources emitting some "other stuff" than simple disposed sewage. strange phenomena can be seen by various imagery dates from 2005 up to 2015.
Richards Bay diffuser (South Africa) - an example GE screenshot by a maximum level of emission:
what it is? -can be pollutant? -sewage? -or some harmless sediment departure process from the heavily shipped bay-waters? -have never seen such before... ...amongst the many other things...(:
I think have find something: sapeolple.com article reports South-African sewage problems while describes underwater sewage outfalls or diffuser ports.
I have placemarked 3 more sites of emission by Cape Town coast, also included OP's site as it seems to fit into story, all set to best imagery dates.
Table Bay Diffuser is one of them:
... updated kmz folder attached to OP.
instant edit: Two more sources (PDF.file#1 from a lecture on lth.se // PDF.file#2 on springer.com) convinced me, question mark can be omitted,
and PressReader.com article has put it to an end with further sites along South Africa coast, Richards Bay included.
This latter source gives also measures and details of the waste water spilled in the ocean (domestic/oil-industry/chemical/etc.): Only "the city of Cape Town marine outfalls can discharge up to 55 million litres of waste water a day."
outfall pipeline under construction (GE imagery, 6/29/2018):
Posted by on 8 May 2017 The pipeline has been towed from Norway to Lough Foyle, where it will be assembled prior to towing to Blackpool for installation in August, followed by trench backfilling and diffuser installation works. The Murphy work barge, LM Constructor, will be used for the marine operations including installing hundreds of large concrete collars and ballast weights needed to ensure the stability of the polyethylene pipeline. The outfall project is due for completion in December 2017 and the pumping station project and park scope runs on well into 2018. The park doesn’t reopen until circa 2019/20.