Oh boy - this is one for the "Duh!" recordbook.
I was shooting wideangle on Thursday in Grand Cayman, and I didn't realize that when I pushed the camera into the housing, the control switched the ISO setting to 1600!!!! That's 3 or 4 stops up from what I normally shoot!
Since I'm not used to shooting the S2 in clear Caribbean water I figured "wow, this water is really clear, I'm getting f16!" Well....no.
For those that are interested in the technical details and would like to see some samples of noise at ISO1600, send me an email or a private message.
And for everyone else - check that ISO setting when you get in the water.
Cheers
James