Recently I've been tracking my SAC with subsurface. I download dives from my Shearwater Peregrine, so all I need to to record is starting and ending PSI (and what kind of tank). I record the starting pressure on the boat, since checking the pressure is part of my pre-dive routine. In warm locations with a compressor on the boat, that typically means a drop of around 300-500 psi when I hit the water. I guess it doesn't matter since it makes the SAC more conservative for planning purposes (if I actually did that...), but it bugs me in some small way. Do people bother trying to correct for that e.g. by recording in-water pressure, or does it just not matter that much?