Answer
These organisms can live at a maximum depth of 10.0 km under the sea.
Work Step by Step
We can find the depth $h$ under the ocean surface where the absolute pressure is 1000 atm:
$P_{abs} = P_{atm}+P_g$
$P_g = P_{abs} - P_{atm}$
$P_g = 1000~atm -1~atm$
$P_g = 999~atm$
$P_g = (999~atm)(\frac{1.01\times 10^5~N/m^2}{1~atm})$
$\rho~gh = 1.009\times 10^8~N/m^2$
$h = \frac{1.009\times 10^8~N/m^2}{\rho~g}$
$h = \frac{1.009\times 10^8~N/m^2}{(1025~kg/m^3)(9.80~m/s^2)}$
$h = 1.00\times 10^4~m$
$h = 10.0~km$
These organisms can live at a maximum depth of 10.0 km under the sea.