The current world record for the deepest scuba dive is 332.5m, set by Ahmed Gabr in the Red Sea in 2014. It took him just 12 minutes to reach that depth, but it took over 15 hours for him to safely ascend to the surface!
The sand in the Sahara Desert is mostly made up of the skeletons of diatoms, a type of phytoplankton that live inside silica housing, who used to live in an ocean above Northern Africa millions of years ago.
The chemical composition and structure of some corals is so similar to our own bones, that they can actually be used in bone grafts. Some alterations have to be made to the coral before insertion, but it is actually beneficial for the patients who require less surgery.
Some starfish suffer from an extremely rare birth defect and are actually square in shape! It can only happen to sea stars with five points and the exact nature of the mutation is still unknown.
The blanket octopus (aka the rainbow octopus) have one the most extreme cases of sexual dimorphism (where different sexes are sized or shaped differently) in the animal kingdom. Whereas females grow to six feet in length, males only grow to be an inch long!
Sea turtles cannot process all of the salt from the seawater they drink in their kidneys. Therefore they secrete excess salt through a gland below their eyes, often giving the impression they are crying when on land
Marine iguanas have trident-shaped teeth that are specially designed for scraping algae off rocks. It gives them the appearance of little hands that wave at you from their gaping smiles.
Boxer crabs use anemones as ‘boxing gloves' to fight off predators. In this form of symbiosis the anemones get free travel and food in return for being used as a stinging weapon to protect its crustacean host
Some species of deep-sea anglerfish engage in a disturbing and bizarre behaviour known as sexual parasitism, where the dwarf males bite into and then fuse bodies with larger females, before spending the rest of their lives stuck together.
Frilled sharks have the longest gestation period of any vertebrate, capable of pregnancies as long as three and a half years (that's 42 months!) and if that wasn't bad enough the litter size can be as big as 15 offspring.