Whether it's a UFO sighting, strange tracks in the forest, or an eerie sound in the dead of night ... underwater microphones, ...

Immerse yourself in the vibrant colors and exotic marine life with this breathtaking underwater scene ... wallpaper ...

When Hans Hartman, a civil engineer, attempted to film the ocean depths in 1917 ... April 1964 explaining how five men will spend the night underwater in this new housing. Image: UPI photo ...

That's exactly the kind of experience offered at The Muraka, the world's first underwater hotel villa. Located more than 16 feet below sea level in the middle of the Indian Ocean with glass walls ...

For seasoned travellers who've seen and done it all, the final frontier involves dipping a toe into the world's best underwater hotels.