Legends and animals from the Cook Islands feature in new mural

A 560-metre plain grey seawall has been transformed into the longest mural in the South Pacific.

The seawall, which sits next to Rarotonga's airstrip, features legends and animals from each of the 15 islands that make up the Cook Islands.

It took 20 months to be completed, well exceeding the expected timeframe of a few months.

Travelling artist Gonzalo Aldana from Mexico, who is the main painter and mural architect, said he is glad to finally have it finished.

"I feel more relaxed now, it was a really challenging project and it was a very long journey," he said.

"I feel definitely very pleased to see the project totally complete."

Aldana said despite the challenges - like the weather which delayed the project - he would do it again.

"It's not just a mural, it's not just to beautify the concrete and that's it, it's more about all the content, the background and the meaning of this great project."

Aldana had to undergo research into each island.

"I was learning a lot about the culture through the investigation… not everything is online, sometimes it was more about opinions of each island.

"It was nice to discover how beautiful the culture of the Cook Islands is."

The work was sponsored by ocean charity Seacology to showcase Marae Moana, the name of the multi-use marine park which extends over the nation's entire exclusive economic zone, covering roughly the area of Mexico.

It was created in 2017 with the purpose of protecting the ocean. Since it was implemented, each of the 15 islands is protected by a 50 nautical mile marine protected area that prohibits large-scale commercial fishing and seabed mining.

Kevin Iro, who spearheaded Marae Moana, said he could not think of a better way to display the nation's ocean.

"The 15 islands, a little bit of our history, talk about our endemic species and obviously our ocean and what unites us as people," Iro said.

"It's just an amazing project and we're getting so many people commenting every time you post online."

Aldana got to talk through the mural with the Cook Islands Prime Minister Mark Brown during its official opening last month.

"It's incredible how through art we can express a lot of things, we can transform the public spaces, but also we can reach the interest of people that we never thought," Aldana said.

"It was really cool to meet the Prime Minister, the leader of this nation."