Due to the curved lens of the waterproof housing for the HD HERO camera and standard def Wide HERO cameras, you will notice a slight loss of sharpness/focus to underwater images.  In video mode with the standard def camera this is not very noticeable due to the lower resolution.  With the HD HERO camera this becomes more evident at the higher resolution.  We have developed a flat glass adapter / housing specifically for underwater use, thus allowing for the same image sharpness that you enjoy with your GoPro camera above water.