The seven-foot long whale swims at full speed into a rocky breakwater in the bay with the slightly smaller seal hanging by its teeth onto its tail fins.

The footage shows blood pour from head injuries that the rocks inflict on the whale on impact but the huge cloud of reddy brown liquid that appears is not blood but ink.

The dwarf sperm whale releases a huge cloud like an octopus as a defence mechanism to confuse predators that attack it like Orca’s and Great White Sharks to escape.

This tragic whale which was suffering deep distress from being in shallow water had been badly injured already after trying to beach itself several times due to its disorientation.

But the seal in a harbour full of hundreds of them clearly thought the whale was an easy meal.

Eye witness Susan du Plessis, 37, who was on holiday and saw the incident said: ‘I thought at first oh my it is a shark and I thought it was trying to get up at a seal pup.

‘People were saying that the seal that was chasing it and biting it and ripping at the back of it as it was protecting its pup and it looked like lots of blood was everywhere in the water.

‘There was a large crowd watching as the seal kept on chasing and chasing then finally gave up but I was later told it was a small type of whale and it beached itself on the rocks.

‘The authorities turned up and a message went out that there was nothing that could be done and a request not to take any more video as they had to shoot it to put it out of its misery.

‘It was an extremely sad situation but the whale clearly had reached the end and although nobody wished it met its end like this it was sadly the kindest thing to do for it’ she said.

The manager of the City of Cape Town Coastal Management team Gregg Oelofse said: ‘These are deep water animals that need deep water for their sonar systems to work.

‘When they get into shallow water they become distressed and disorientated if they are in depths of less than 20 metres and this is what happened when it got into the harbour.

‘It was best described to me like a human being in the pitch black being in a cricket ground and all the floodlights get turned on and off alternatively and you panic and run in all directions.

‘The dwarf sperm whale was similarly distressed and panicked and had become highly stressed and with the seal chasing it swam up onto the rocks and had beached and hurt itself.

‘The whale released ink which is a defence mechanism but the seal would quickly have realised that it was not a target and left it alone but the whale beached itself on rocks.

‘There was nothing that could be done and the whale was euthanized in accordance with the marine mammal protocol by the Society for the Prevention of Cruelty to Animals.

‘It is always tragic when that has to be done but there was no hope in this case’ he said.

The SPCA’s Belinda Abrahams said: ‘Our hearts sunk when we arrived because this Dwarf Sperm Whale was extensively injured and weak and no doubt suffering immensely.

‘According to research these whales often beach themselves when they are too sick or injured to swim and the currents carry them ashore to die a slow agonizing death.

‘We knew that returning this whale to the ocean would not be successful and would only add to the stress, pain and exhaustion that this animal was already experiencing.

‘We had no choice but to do the right thing for the injured whale and the only way to end this whale’s suffering was humane euthanasia which was a very difficult decision,’ she said.

Dwarf sperm whales are rarely seen at sea and dive to depths of several thousand feet.

Adults average eight feet long and 450lbs and eat fish, octopus, squid and crustaceans.

It is not known how many of the slow moving whales exist as they are usually only found when washed up on shore and their greatest predator is the Orca and Great White Shark.

To escape them they release a reddy brown ink cloud from their anus that can spread to 100 square metres which blinds the eyes of their attackers and affects their sense of smell.

Cape fur seals grow to a similar size to dwarf pygmy whales and share the same diet and also fear the same predators with killer whales and great whites seeking them out.

The body of the dwarf sperm whale was taken away to a marine laboratory for research purposes.