Cheers for the final vote Pete.
Spent last night lying in a hospital bed thinking of what to set as the theme for August. Looking through the past competitions, I couldn't see either of my choices (Black&White / Silhouette).
I like B&W as it can add a sense of mystique to a good shot, or, normally in my case, rescue a bad shot. Hopefully, both themes should work in blue/green/warm/cold conditions. The examples I've chosen show the sort of shots I'm thinking about.
For the first one, liked the positioning of the diver and Manta, but in colour it didn't work. Making it B&W definitely improved it.
For the second one, I was trying to get the sun ball behind the diver, and have the diver properly lit, but set the strobe output to minimum rather than full However, I liked the resulting silhouette.
I'll call a halt to posting (if anyone does) on the evening of 31 August.