Manual focus settings underwater and with WA

Hi!

I have a Sony DSC W12 in an Ikelite house. I can set the focus manualy in a few steps (0.5, 1, 3, 7, inf).

If there a way to recalculate these steps when using it under water with and without WA-lens (x0.6). What focus depth could I expect using F2.8, f7.9mm(38mm) 1/1.8" CCD.

/Martin

Dont know how to calculate these things but I would just take down a ruler and photograph it at 45 deg. Then work the answers out on the computer screen.