Pez,
Thanks for the link. My old Subsea 150 is a 150 W/S non-ttl strobe with io connector and slave sensor. It's no longer made. It uses a 510 V photgraphic battery at about $100 a pop for about a season's use. The C5050 housing has a diffuser to negate the on-camera stobe backscatter and effect but may trigger the slave unit on my strobe. Of course, that will not help if the C5050 uses a pre-flash for either exposure calibration or pre-focus. The TTL type thingy you linked me to would be absolutely necessary if the camera either pre-flashes, does not flash, or is buffered too much by the diffuser to trigger the slave unit on my strobe.
The wide-angle attachment sold by B&H and others is made by Sea & Sea, I think. It brings the lens to 20mm FL coverage and screws onto the existing port from the outside so it can be taken on and off U/W. I think it's probably worth the money and was wondering if anyone had found a better source than B&H. I'm currently using a 15mm on the Nikonos and like it a lot.
Mark