In prep for the Seychelles trip, I have bought a DiCaPac WP-410 for the Lumix camera. I got it for £17 from ebay (including the registered post from South Korea) and it arrived today. Luckily I had the camera in my work bag, and we have an onsite pool, so I will be conducting initial tests later today.
This is one of the test shots with the welding filter. 261 seconds, and still a couple of stops underexposed. Longer exposures are not handled well, the K100D suffers from reciprocity failure and the image actually gets darker with longer exposures. So, not an outright success. I think it is perhaps too dark, but the concept is good. Not sure if I should try a lower shade welding filter, or just stump up for the real deal.
The welding filter arrived from eBay yesterday. Did not get much of a chance to try it out. It is slightly green, but initial tests look like it will be correctable using the spot white balance. Hopefully will get a chance to try it out this evening afte work.