Latest official estimates are that only 55 Maui's dolphins older than 1 year remain in the wild.
"The Maui's dolphins are like the Kiwis of the sea, there's nothing like them," said McDell.
"We're surrounded by water that is so accessible, therefore we can easily develop an appreciation and love for the sea and hopefully that need to protect it for whatever reason works for us all."
She recorded Son of the Ocean last month at Auckland's Roundhead Studios.
McDell wanted a choir of young Kiwis to boost the singing and held online auditions to make up the 55 - one member for each surviving Maui's dolphin.
The 23-year-old said she was a "passionate advocate for ocean conservation". She's a surfer and diver, and lived on a sailboat in the Mediterranean when she was a child.
She is also an ambassador for Surf Life Saving NZ and volunteers as a lifesaver at Pauanui.
Creating Son of the Ocean is McDell's contribution to conservation movement WWF New Zealand's new Challenge 55.
"My goal is to raise awareness for the rare Maui's dolphins and to spark conversations around what we can be doing to keep our oceans healthy for generations to come," she said.
"A song about Maui's dolphins can get people's attention, asking for more protection of the species."
Proceeds from iTunes' downloads of the song go towards WWF's efforts to save the Maui's dolphins, said Peter Hardstaff, of WWF NZ.
Six years into a promising music career, McDell is a strong believer in social media driving campaigns that combine music creativity and conservation.
Her social media following, known as the Gypsy Pirates, includes 202,700 Facebook followers, 28,400 on Twitter, 44,100 Instagram followers and 83,190 YouTube subscribers.
"Online content can inspire young people to get outdoors and figure out for themselves why it's important for us to look after our land and sea," said McDell.
"It's more helpful to give people a reason to care rather than just telling them they should."
The Challenge 55 campaign encourages people to develop their own fundraising projects that will support the WWF's work.
"We can save Maui's dolphins if urgent action is taken," said Hardstaff.
"The Government needs to remove set-netting and trawling from Maui's dolphins habitat and support affected fishers to move to dolphin-friendly fishing methods."
