New 3-D optical underwater images are presented. The 3-D images are recorded in fresh water and brackish sea water (salinity 15‰), at 4- to 5-m range. For the first time, underwater 3-D images are computed by our new algorithm, which applies the method of weighted averages on a sequence of 2-D images. It is proposed that 3-D gated viewing images can be recorded at any contrast level between 0 and 100%. A novel and dynamic way of measuring the depth of gating is presented. A novel correction for gated viewing 3-D imaging is presented. For the first time, an exact solution of the depth of gating is proposed for a rectangular laser pulse.