A 10.2m male humpback whale that stranded at Hickman's River in East London on Monday, has died.
East London museum principal scientist Kevin Cole said the animal presumably died of organ failure.
On Monday, Cole told News24 that his team had tried its best to get the whale back to sea, but it had taken a lot of strain.
He said there was a slight chance it might have been able to float out during high tide.
"But there was just not enough water and it remained stranded," he said.
"When I arrived at the beach at sunrise [Tuesday morning], the whale had sadly already passed on."
Cole said the whale had seemed to be in reasonable health and rather young.
"The whale had no trauma to the body, it didn't look emaciated, though other cetacean researchers have commented that it looked quite thin," he said.
Whale migration season has just started and Cole suspects the whale may have made a navigational error.
"The area is very deep and cuts into quite shallow water. We've had a few strong tidal surges in recent days. The whale came into shallow water and possibly panicked and became disoriented," he said.
The whale was estimated to weigh approximately 16 tons.
In 2016, a fully grown 22m-long, 40-ton fin whale stranded and died in the same area.
Cole said he spent most of Tuesday taking measurements and blood, muscle, blubber and skin samples, which will be sent to the Bayworld marine mammal collection, curated by Dr Greg Hofmeyr.
"At some stage, pathology will be done on the samples and tests for DNA," Cole said.
He planned to continue conducting tests on Wednesday.
The carcass will remain in the area as it poses no health hazard and the smell shouldn't be a problem.
"Normally if the carcass is in an area close to a bathing beach, then an effort is made by the municipality to remove it. But this whale was stranded in an area that is isolated and not frequented by many people for various reasons," Cole said.
"Once I open up the whale, it will decompose rather quickly. Over the next two months these nutrients will be returned to the sea."