Thanks for your comments. I also like the second shot, in fact, the first one is blah but the shrimp is very sharp! If I had any Photoshop skills at all, which I don't, I might try swapping the two shrimp. Thanks also for the test suggestion - I will have to try that.
I usually shoot at f16 or higher for macro (which has been 95% of my experience) but I read somewhere that this WA lens does not perform well at smaller apertures. I will have to experiment to find out if that is true. I should have done it on this dive!