To determine the efficacy of particle size estimation of four different methods: LISST (Laser In-Situ Scattering and Transmissometry) and LOPC (Laser Optical Plankton Counter) as in situ methods, Coulter Counter and light microscopy as in vitro methods, we examined the particle size distributions measured by each method and their variations for samples from Tokyo Bay.
The measurement value of particle volume of LISST is a little higher than that of LOPC. The volume of the particle size between 7.33 μm and ca. 20 μm in LISST was in accordance with Coulter counter and microscope. The correlation coefficients between particle volume by Coulter counter and particle quantities of suspended solid materials, Chl. a, and beam attenuation coefficient had the highest values in all methods.
We were able to make a particle size distribution over a range of 7.33-3,355 μm by coupling the results of LOPC with LISST. The particle size distribution of the inner part of Tokyo Bay in May has two peaks at 17 μm and ca. 400 μm. The two peaks were identified as related to a species of diatom, Prorocentrum minimum (mean diameter; 18.4 μm)and flocculation particles by microscope observations, respectively.
It is possible to determine the in situ particle size distribution of a wide range of particle sizes in seawater by using LISST and LOPC.

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Sea-bottom images of stereographic pair for 3D viewing are easily obtained if 3D video camera is set in pressure case with transparent window or using 2 sets of ordinary video cameras.
In case of 1 set video camera, we can obtain images of stereographic pair for 3D viewing by taking continuous or overlapping shots during the horizontal movement of submersible.
3D viewing of sea-bottom produces real feeling in detail, but sometimes it causes too much exaggerated and non-real 3D image.
We developed a method to calculate rough sea-bottom undulations, and applied it to photographs obtained during the submersible Shinkai6500 dive#1075 of the YK08-07 cruise and video images during ROV Hyper-Dolphin dive#835 of the NT08-09 cruise as examples.
After reading the corresponding points in the stereographic pair images, the depths of those points were estimated using the image size, the camera altitude and the distance of the left and right camera locations (parallax).

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