The great unknown is just under the sea, miles under the sea that is. There are still places unknown to humans and it is in places where we cannot survive. The pressure under water is just too great for us to go so we need complicated equipment that can withstand the immense pressure.
There is also not a lot of light under a couple of miles of sea water so high powered lighting is required as well to see. There are many species of fish that are discovered daily and we are just touching the surface of what is under the deep blue seas. Children should learn about these amazing species of creatures as well as their environment in a study called oceanography.
There is nothing more exciting than learning about animals that have been around for a long, long time in environments that are so distant from humans, one would never guess something would live there!