Even using tripod I found that 2 sec timer does not work unless it is a very heavy tripod. In normal ones the vibration of camera after pressing shutter release dies down in about 3-4 sec with the center column down. With the column up it can be around 7 sec. this means the camera would be shaking even when the timer ha timed out and photo can be ruined.

Using a cable release is the best option even with 2 sec timer. Else use 10 sec timer.

One other thing I have done (and not often as it’s time consuming) is to enlarge the photograph in Photoshop to a pixel view and change some of the pixel colors. I shot a flower on a black background and was very hapy with it except for one small area of focus right at the tip of a petal. I changes a few pixels to black instead of blurry and got a significantly better image, infact it was a top scoring photo at the club I belong to.

As an ex diving photographer, the best method was to ensure you are neutrally buoyant (when you breathe in/out you move up/down). Once you’ve got this when you take the shot, hold you breath, if you are mid stream not a lot else you can do. Obviously at the sea bed you can use a rock or something else dead! Holding breath at the point of shutter depression should help.