I want to find a device to observe the underwater situation, similar to a periscope, except that I am on the shore and a lens is underwater.

1, the refractive index difference between water and air is too big to see far;

2. Most natural water bodies are turbid and cannot be seen clearly;

3. The periscope's field of vision is too small for the fish to swim fast.

So the idea is good, but there is no suitable equipment. If you want to see the activities of fish, suggest a fish tank. ...