Submerged Seawater Lift Pump Elevation (below sea level)

[DoraeS]

Hi,
I need to design a submerged seawater lift pump.
Can anyone tell me what should be a general "margins" for the lift pump bottom? I have the following design steps as below:

a. Find the lowest sea trough (in this case it is -9m)
b. Find the SW Lift Pump length (estimated 2m in this case)
c. Find the required NPSHr (assumed 2-4m in this case)
d. Find the pressure loss for SW lift pump inlet strainer (assumed 1m)
e. Find the pressure loss due to the SW lift pump caisson (assumed 1m)
f. Based on calculations, NPSHa is 20m which is more than NPSHr.

If I add up the above I have total required elevation of: 9 + 2 = 11m
I know we also need to find out the corresponding Seawater temperature at that elevation if it is suitable for our topsides cooling requirements. Let's simplified it here as this is a shallow water platform hence the SW temperature is not changing so much with elevation.

Can I then select the SW lift pump to be located at -11 or -12m?
I would like to know if I miss something here.

Thanks.