【Watch Salyut 7 Online】

The Watch Salyut 7 Onlinebiologists were ecstatic.

A deep sea mission, undertaken by the Ocean Exploration Trust aboard their 223-foot vessel (E/V) Nautilus, recently spotted four nautilus individuals. Creatures similar to these modern-day nautiloids — swimming mollusks residing in large shells — have been around on Earth for some 500 million years, evolving much earlier than the dinosaurs.

Today, the creatures aren't easy to find. The Ocean Trust explorers have endeavored into the deep sea for 15 years and taken over 1,000 dives with their remotely operated vehicle. But these are the first nautiloids they've spotted.

"It's finally happened," a member of the exploration team said at the beginning of the footage, shown in the video below.

This ocean footage, fortuitously taken on the last "grand finale" dive of their season, was captured between 720 and 1,230 feet (220 to 375 meters) underwater. The nautiloids were swimming in a south Pacific Ocean channel off of Palau.

There are six living species of nautilus alive today. They are rarely seen living fossils, and such sightings are only made possible on deep dives, typically with robots. These expeditions turn up completely novel species, too.

"We always discover stuff when we go out into the deep sea. You're always finding things that you haven't seen before," Derek Sowers, an expedition lead for the National Oceanic and Atmospheric Administration's Ocean Exploration mission, previously told Mashable.

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Ocean research organizations are now vigilantly documenting and mapping the deep sea. Scientists want to shine a light — literally and figuratively — on what's down there. The implications of knowing are incalculable, particularly as deep sea mineral prospectors prepare to run tank-like industrial equipment across parts of the seafloor. For example, research expeditions have found that ocean life carries great potential for novel medicines. "Systematic searches for new drugs have shown that marine invertebrates produce more antibiotic, anti-cancer, and anti-inflammatory substances than any group of terrestrial organisms," notes the National Oceanic and Atmospheric Administration.

At times, the search for what lies below leaves scientists awestruck.

"It's so beautiful," another team member marveled in the video. "Let's stay here forever."

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