Dolphins can see in the dark

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AND THEY SEE WITH THEIR EARS
 
Dolphins have very good eyesight. They can see underwater but they cannot distinguish between colours, for them everything is green ! 
On the other hand they can make out different types of grey. 
Their eyes are a little bit like cats' eyes.
However, it is not with their two eyes that they see the best but with their ears. They haven't got ears like us, theirs are small and inside their skull. They vibrate when the jaw vibrates.

Often they dive to the depths of the sea where light cannot reach. It is completely dark but the dolphin 'hears' the things around him as clearly as if he were in daylight. The dolphin uses sonar like a bat.

The noise produced inside the blowhole comes out of the dolphin's 
forehead and not through its mouth
 

The dolphin lets out very brief, small cries called 'clicks' in the direction of a fish. The sound rebounds off the fish and sends back information to the dolphin about its shape. In this way the dolphin can 'see' even though it is pitch black.

Even better than this, if he wants to, he can direct the noise even more piercingly towards the fish. The sound penetrates its body and the dolphin can see its bones, its stomach, its eggs and the heart of its prey, just as if he were using X rays!

If the dolphin makes the noise MUCH STRONGER it can even stun the fish from a distance. This is the 'deadly cry' of the karateka !