Vitreledonella Richardi, known to its friends the glass octopus, is a stunning, bioluminescent creature, but you might just have to take the word for it. The glass octopus can grow to a length of about 18 inches, but is almost as diaphanous as the tropical or sub-tropical waters in which it makes its home. Vitreledonella richardi can also live at depths up to 13,000 feet, so is rarely, if ever, seen.