What depth in water is 10 ATM?

Every 10 metres of water adds 1 ATM, so a depth of 10 metres is 2 ATM (the atmosphere of pressure at the surface plus the pressure of 10 metres of water). 10 ATM is reached at 90 metres, or approximately 295 feet (10 metres is approximately 33 feet).

(The 1atm/10m is true for salt water at 15C; actual pressure/depth depends on water - fresh Vs salt - and temperature, but 1atm/10m is a good guideline for most purposes.)