Question on S1 sync for TTL in Sea and Sea Housing for Sony a7iii

Wow, that seems harder than it should be! I make a living looking things up on Google (I'm an IT consultant), and I can't find any instructions online either. I take it this is a very new product?

I'd write an email to Sea & Sea support about this. I suspect the manufacturing plant in China is faster than the documentation staff.

Looking at this picture of the parts:

https://www.aditech-uw.com/en/shop/3242-sea.html

and combining that with my limited experience of failed-ttl-trigger-installations, I'd say this.

It appears you have a big battery compartment that is meant to fit into the housing somewhere.  I have no idea exactly where, but it looks like it has a long wire to give you some flexibility in locating.  I suspect there is only one place in the housing where it will fit, and it doesn't seem to have a mounting lug, so look for a place to just stick it out of the way for now.

There is clearly a connector that slides into the hot shoe of the camera (last).

There is what looks to be a cover to go over the circuit boards in the prism area of the housing.   That would go in after the boards.

It seems odd there are two circuit boards.  I guess they need to be stacked, and it seems clear that one is shaped to go into the prism area.   The other I don't know.  Possibly it fits in the prism area too, but possibly it doesn't and has to go somewhere else, like the batteries do.

Which leaves the LED board that actually puts out the light.   That board should have a clear installation point where the LED's are pointing to the fiber optic connections on the housing, inside the prism area.   That should go in first.

I think if you play around a bit, you'll find one way it all fits.

My experience:  I bought a TTL trigger from Bluewater Photo for my D810 in Nauticam housing.   When I got it, the installation instructions did not match my housing as the housing had changed a bit.  There are no longer mounting screws holding in the old optical prism (for the pop-up flash), so I was not able to unscrew the old prism and replace it with the trigger.  Apparently my prism is glued on.   I was unable to remove it without risk of damage, and Bluewater could never tell me how to do it.  After dithering around without any good suggestions for a few weeks, Bluewater told me the part is beyond their return window, so I'm stuck with a new ($400) TTL trigger that cannot be used.

If you don't get satisfaction on the trigger, return it quickly and wait for one that comes with instructions.