The president of the Seychelles has made a plea for stronger protection of the “beating blue heart of our planet”, in a speech delivered from deep below the ocean’s surface.

Danny Faure’s call for action, billed as the first live speech from a submersible, came during a visit to an ambitious British-led science expedition exploring the Indian Ocean depths.

“Oceans cover over two-thirds of the world’s surface but remain, for the most part, uncharted. We have better maps of Mars than we do of the ocean floor,” Faure said. “This issue is bigger than all of us, and we cannot wait for the next generation to solve it. We are running out of excuses to not take action, and running out of time.”

The president was speaking from a manned submersible 120 metres (400ft) below the waves, on the seabed off the outer islands of the African nation.

Wearing a Seychelles T-shirt and shorts, Faure said after his speech that the experience was “so, so cool”. It had made him more determined than ever to speak out for marine protection, he said. “We just need to do what needs to be done. The scientists have spoken.”

The oceans’ role in regulating the climate and the threats they face are underestimated by many, even though, as Faure pointed out, they generate “half of the oxygen we breathe”. Scientific missions are crucial in taking stock of underwater ecosystems’ health.

Small island nations are among the most vulnerable to rising sea levels caused by climate change. Land erosion, dying coral reefs and the increased frequency of extreme weather events threaten their existence.

During the expedition, marine scientists from the University of Oxford have surveyed underwater life, mapped large areas of the sea floor and explored the depths with manned submersibles and underwater drones.

Little is known about the oceans below depths of 30 metres, the limit to which a normal scuba diver can go. Operating down to 500 metres, the scientists were the first to explore areas of great diversity where sunlight weakens and the deep ocean begins.

By the end of the mission, researchers expect to have conducted more than 300 deployments, collected about 1,400 samples and 16 terabytes of data and surveyed about 25,000 sq metres (269,100 sq ft) of seabed using high-resolution multi-beam sonar equipment.

The data will be used to help the Seychelles expand its policy of protecting almost a third of its national waters by 2020. The initiative is important for the country’s “blue economy”, an attempt to balance development needs with those of the environment.

“From this depth, I can see the incredible wildlife that needs our protection and the consequences of damaging this huge ecosystem that has existed for millennia,” Faure said in his speech. “Over the years we have created these problems. We can solve them.”

About 5% of the world’s oceans are protected. Countries have agreed to increase the area to 10% by 2020. But experts and environmental campaigners say between 30% and 50% of the oceans outside nations’ territorial waters should get protected status to ensure marine biodiversity.