"Pink dolphin, two o'clock!"
It takes a moment to orient myself to the analog directive, but I manage to turn and spot it in time. A few yards ahead of me in the South China Sea is a flash of pink dorsal fin.
I have seen my first pink dolphin.
And they're not just pink, they're bubble-gum pink. So pink you would think it's a Sanrio marketing ploy, but it's the real deal. This is the Indo-Pacific humpback dolphin which can be found in Southern China, the Indian Ocean and Western Pacific.
But only the ones here, in China's Pearl River Delta, are pink.
Samuel Hung, scientist and activist with the Hong Kong Dolphin Conservation Society, tells me: "We are not sure why they're pink in color. When they're dead, they're white. We think it's a blushing effect, and that's how they regulate their internal heat."
The dolphins are grey when they're born and gradually become pink as they mature. But these extraordinary creatures are dwindling in number. In the entire Pearl River Delta, their population stands at around 2,500. Off the coast of Hong Kong, they are only 100 pink dolphins left.
It's not hard to understand why. My journey to see them begins off a small port near Hong Kong's busy international airport. It's a highly congested area where runways, highways and railways collide - much of it built in dolphin habitat.
My guide, Janet Walker of Hong Kong Dolphinwatch, says the declining population is making her job more difficult.
'The great, amazing sightings that we usually see regularly have been fewer and further between," Walker tells me. "We probably have 3 to 5 on an average day, where we would have seen 6 to 8 several years ago."
Aboard the Hong Kong Dolphinwatch cruising boat, I am with a handful of other curious animal lovers including a little girl from Taiwan. She cries out in joy for what she thinks is her first sighting. Alas, it's just some Styrofoam boards floating by.
"Pollution is a main thing," Walker points out. "We dump 400,000 cubic meters of raw sewage every day in our harbor. That's about 400 truck loads."
As we head further out to sea, we see the massive container ships in the distance. Sea traffic is yet another man-made factor threatening Hong Kong's pink dolphins.
But when we reach a couple small fishing boats, our sea safari pays off. We come across a family of pink dolphins gathering to feast on the throwaway catch.
The sightings are breathtaking. I manage to spot at least five individual pink dolphins, and follow them as they swim around our boat and into the distance.
But this beautiful spectacle is facing even more threats. Conservationists say plans for another airport runway and a new bridge between Mainland China and Macau will further encroach the dolphin habitat. Hong Kong's government says the plans were approved after it passed the required environmental impact assessments.
Janet Walker has been looking for, and looking after, the territory's resident dolphins since she joined Hong Kong Dolphinwatch in the mid-90s. I ask her if our pink dolphin sighting is something that can be repeated a generation from now. The prognosis is grim.
"If we're talking 25 years, I don't see us being out here then."