The ocean covers almost ¾ of our planet. It should come as no surprise, then, that much of this gigantic body of water is still unexplored and undocumented. Most scientists put that amount at 95%.

Here are four fascinating examples of how the ocean continues to be a mystery.

1968: Year of the Missing Submarines

By their very design, submarines are meant to never be seen. However, after 1968, four departed into the depths without ever being seen again. They didn’t resurface and no expedition has ever located their final resting places.

What’s even more interesting is that each of these submarines was from different countries. They were:

  • The INS Darak (Israel)
  • The K-129 (Soviet Union)
  • The Minerve (France)
  • The USS Scorpion (U.S.)

On the other hand, one of the leading theories cites this very fact as its foundation. Perhaps there was a secret battle going on under the waves that we never knew about. This theory often views the USS Scorpion and the K-129 as being the two main players, potentially locked in a Cold War standoff.

What we know for sure is that, despite the size of these ships and their respective governments’ knowledge of their areas of operation, the ocean refuses to give them back.

Japan’s Sunken City

In 1986, a scuba diver off an island just to the South of Japan discovered underwater formations of sandstone unlike any he had ever seen. They featured smooth planes and straight edges.

When his discovery made it back to the rest of the world, theories abounded. Many scientists explored the area and concluded that this was once an actual city; it seemed to feature five temples, a castle and a stadium, complete with a triumphal arch. The main theory is that a giant earthquake submerged the city.

The Super Shark

Biologists are constantly tagging white sharks to learn as much as possible about these fascinating – but mysterious – fish. These tags can be used for a number of purposes; among them: tracking the shark’s movements throughout the ocean.

In 2014, scientists were in for quite the shock when they retrieved one of their shark tags. Well, to be fair, it wasn’t retrieved so much as it was washed up on the shore. The nine-foot shark it had been implanted in was nowhere to be seen.

When the scientists uploaded the information from the tag, they were in for a shock. It showed that the tag suddenly underwent a rapid increase in temperature followed by an equally abrupt descent 1,900 feet below the ocean’s surface.

This only provided one very chilling explanation. The tag’s temperature change was due to another animal’s digestive system and the descent was because whatever ate it was returning to the murky depths from whence it came.

The best – albeit, still terrifying – explanation is that the nine-foot shark was attacked by an even larger one. Cannibalism is not rare amongst this species, but the shark responsible for this attack would have to be at least two tons.

The Bermuda Triangle

This probably doesn’t come as too big a surprise, does it?

Well, it’s actually not a part of this list.

That’s because there is no mystery. The Bermuda Triangle is the ocean’s urban legend: perpetuated year after year without any real evidence. If you take the same size of the triangle and apply it anywhere else in the world with the same amount of traffic, there is no significant difference.

Many of the incidents attributed to the Bermuda Triangle’s mysterious forces can easily be attributed to the area’s numerous tropical cyclones.

Sloppy reporting has also boosted the Triangle’s myth. Many ships and planes reported missing eventually returned elsewhere.

This is just a tiny sample of the many, many mysteries the ocean keeps from us. As we discover more about it, expect that we’ll actually find more inexplicable features in its depths.