You sometimes see and do amazing things that give you renewed faith in the world.

But sometimes you find yourself witnessing something that creates another little crack in your heart.

Yesterday, I saw such a thing.

A friendly, well known dolphin, famous for her love of tail walking, boats and people was killed.

Billie, the bottlenose dolphin first came to the attention of Adelaide residents when she was photographed by the local newspaper swimming with racehorses, exercising in the Port River.

She had previously spent some time at Marineland - a poor example of an indoor "sea park" here in Adelaide, which thankfully, has since closed.

Billie's life was full of drama. After being released from Marineland, with a number 3 tattooed on her dorsal fin, she became repeatedly trapped behind a lock in a polluted waterway called the Patawolonga.

Every time local wildlife experts came to her rescue only for her to become trapped again several days later.

She was eventually relocated to the polluted Port River. It became her home.

She gave birth to four babies. Only two survived - it's likely the ones that didn't make it were poisoned by the pollution downloaded in Billie's milk.

Billie was seen nudging her dead babies around the river, seemingly trying, in her own way, to revitilise them, to bring them back to life.

It was heart wrenching to watch.

Billie was so famous, she was the focus of two children's books, her photos regularly graced national and international newspapers and her personality endeared everyone to her.

Many people marvelled at the spectacle of Billie tail walking (a behaviour she learned at Marineland), jumping in boat wakes and approaching boaties with that ever present dolphin smile.

In recent weeks, researchers noticed that Billie was looking thin and ill.

So vets took a sling and a host of volunteers into the shallow waters of the Port River to take a closer look.

She swam into the sling, and was euthanized.

Vets said her condition was very bad, and it was only humane course of action - renal failure was suspected.

I watched the footage of this happening, and couldn't contain the tears.

It was up to me to share the news with Adelaide Viewers live to air, and to be honest, I had to choke back the tears. It was possibly one of the most difficult things I have ever had to do in my fifteen years of working in television.

Billie, who was only 20 years old, dolphins can live until they're 50 or even 60, will now undergo an autopsy. I have my own suspicions about her demise.

Like many other dolphins, the Port River pod survive in a polluted waterway, where effluent, storm waters run off and industrial waste provides a daily top up to the already filthy river.

One of the dolphins, which died several years ago, was found to have the highest levels of p.c.b's (a chemical that stays in fat), of any dolphin in the world.

The mortality rate of baby dolphins is high, as these toxins make their way to the calf via the mother's milk and cannot cope with such high concentrations of pollutants.

So, these beautiful animals exist in a cesspool which the State Government pronounced as Australia's first "dolphin sanctuary" about 8 years ago.

The government got a lot of mileage and feel-good media exposure out of its pledge to look after Adelaide's dolphins. Even I was convinced our dolphins would benefit.

But I wonder what has really changed?

There are now two dolphin rangers who patrol the area on an irregular basis in a rubber dinghy. The Government will tell you that discharges aren't as bad as they used to be and that industry is slowly cleaning up its act.

But the fact is that effluent, stormwater and industrial waste still go into the river.

More land is being developed along its banks, and the population is increasing, boat traffic has also increased dramatically, more people are fishing the river and dolphin entanglements in fishing line remain a regular occurance.

What kind of sanctuary is this?

The autopsy results from Billie are likely to be completed within the next couple of weeks. I'm betting they find high levels of some kind of heavy metal or chemical in her system.

Whether that information ever gets released to the public though, is another thing.