Question

The pressure due to atmosphere is very large, then why are we not crushed

Answer 1

Because the atmosphere also pressurize the body. Diving down 100 meters will pressurize the gasses in the body and they will compress, like the air in our lungs and if the lung volume get below half a litre the lungs can get partly filled with blood plasma. But sorry no bone crushing. But if you take a big breath and hold it while you ascend from 100 meters to the surface, your ribs may start to break