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In brief, it is not possible to directly electrically wire two Nikon SB800s for iTTL use. Through testing it became evident that the water medium hampered the light signal required for wireless communication between two housed SB800 speedlights. I used two SB800s in Fantasea clear polycarbonate housings with homemade optical cabling mounts. One SB800 is set as master and the other as remote; both in iTTL mode.

The first SB800 (master) is electrically wired to the housing using the Nikonos style (Sea and Sea) sync cord supplied with the housing.

The second SB800 (remote)   is where things become interesting as this speedlight is optically triggered from the master speedlight.

In clear polycarbonate housings I had hoped that the two SB800s would be able to communicate wirelessly. While this worked fine topside, underwater testing was not successful as there was insufficient signal to fire the remote. To solve this I routed a .75mm single strand fiber optic cable from beneath the strobe lens on the outside of the master's housing.

The receiving end of the optical cable is positioned outside the housing and adjacent to the SB800 sensor which is located on the right hand side. Both ends of the fiber optic cable are sunk into plastic screws mounted onto velcro which are fixed to the outside of the housings using mated velcro with adhesive backing.

Both strobes are set to iTTL. The intensity of master or remote can be controlled from the rear panel of the master. Focal length of the strobe heads can also be adjusted from each strobe although I have found that at 105mm, light is too channeled for the signal. I tend to use the built-in diffusers for WA.

The scorpion fish pair image shows shadows cast from two directions demonstrating both strobes active. While use of vendor supplied optical cable and mounts was not successful, my homemade mounts did function quite nicely.

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