Researchers claim we know about less than 1% of our deep seas here on Earth, raising concerns over possible deep sea mining.

The deep sea refers to the part of the ocean below 200 meters (656 ft.), at which light begins to disappear. Despite making up more than 90% of the Earth’s marine environment, much of the deep-sea ecosystems is still a question mark for researchers.

In a new study published in Science Advances, oceans researchers say that just 0.001% of the deep seafloor has been visually observed. The findings highlight the potential for a lack of understanding of ocean biodiversity.