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Pressure of fresh water= 1,000 kg/m cubed

g= 10N/ kg

1,000 mbar= 1 bar= 100,000 Pa

5. Change in pressure= h*p*g
250,000 – 100,000= h* 1000 * 10
h= 15m

If he was diving in sea water then, h would be more as from the equation:
Change in p= same, g= same, p= less so h= more

6. p=0.42 g/ cm cubed= 420 kg/ m cubed
Change in pressure= h*p*g= 50 *420*1.4
Change in pressure= 29kPa
1.6 bar= 160,000 Pa 29,000 + 160,000= 189,000 Pa= 19 kPa